Ok Sofa, here is the basic rundown of what you need to convert your cockpit into an actual flyable simulator. And sorry for the week of delay, I've been really busy with my own cockpit building efforts.
First, take a look at Lockheed Martin's Prepar3D Simulator. I will link everything at the bottom. P3D is the next evolution of Microsoft Flight Simulator X, but is rather MS-ESP where they have redeveloped all the code for modern CPU/GPU hardware. It is not publicly advertised but is publicly available for sale. You'll want the $60 educational license since you are not building any sort of FAA cert trainers like I do. Next, you would need a controls assignment and calibration utility (CACU as I call it) like FSUIPC. I have a free guide on my Hangar Talk page which tells you how to use it. This program allows you to assign physical controls to interface with the simulator. Some are also using LUA these days but it's a little more complicated than you'd need to get going and to have a very realistic experience.
Next, you would need a USB control board (or two) which can interface with various control types, meaning spring return push buttons (momentary type), or spring rocker type of momentarys, or pulse type inputs for locking non-spring return on/off type, etc. You would also need a control board for potentiometers for X-Y axes for pitch and roll, dynamic braking, rudder yaw, etc. You could build self made joysticks, or yokes, etc as well self made rudders, throttles, etc.. but you'd probably want to get cheap used stuff first just to figure it all out, then self-build things as needed to complete a more sci-fi look. Ultimately you would want to mechanically link the yokes and rudder pedals.
Now, on to the panel. Because you are emulating the real "sci fi" panel you need to figure out how to use what you have but assign real world functions to the switches via the CACU. If for example you have a button that does nothing, or is a static piece of plastic, it would need to be replaced with a real button that can be soldered to inputs on the USB board. Secondly, consider the fact that aircraft commonly receive avionics updates as time and technology evolves so either consider various panel upgrades or just option to build a whole new "auxiliary" main panel specifically made for interfacing into a flight / space simulator. What I mainly mean by this is you will obviously need some sort of visual displays to show the core flight instrumentation and or will need to use some hardware based analog gauges for what are commonly called the "sacred six" or "six-pack" gauges which are: attitude indicator, heading indicator, altimeter, airspeed indicator, vertical speed indicator, and turn coordinator. Other gauges would be Vor 1, Vor 2, but all of this is all rolled into one with any modern "glass cockpit" in any jet. Buying all theses gauges as actual hardware items can be very cost prohibitive as each one will cost up to $300 or more and must each be wired up, configured, calibrated, etc. All of that takes time, patience, and a good amount of pre-knowledge of what needs to be done, and how to do it. Therefore I would primarily suggest looking at various virtual options such as using virtual 2D panel sets and virtual gauges via an iPad or small LCD screens up to 20" maximum for your specific application. I think 17" would probably be ideal for you.
For example; I like to use two 24" touchscreens in a general aviation twin engine simulator as this allows for a completely virtual panel that can represent many different aircraft and is done so in true 1:1 scale with the real world counterparts. In my case the entire panel is virtual with some tactile switches on the sub panel under the control yokes. Regardless of the screen size, if going this route I could help directly as files can be emailed back and forth, artwork created, etc. I am currently working on a StarTrek shuttle project where all virtual gauges will look very "trek" but will all have real world functionality. I also want to do this for a TRON panel set as well. So, the same thing can be done for any Star Wars craft and could be a relatively easy switch out if you are essentially embedding different artwork into the same XML or C++ gauges. What I would envision for the Falcon would be a modified panel with two small screens that perhaps pop straight up vertically out of the existing panel via some small servos which push up the screens with a rack and pinion gear. The left (pilot side) screen would display the main EADI / EHSI and the right (copilot) side would display engine EICAS data and maybe a traffic radar. These could even be small 17" widescreens or maybe even as small as 15" if desired. I think anything over 19" would probably be too large. The two displays would therefore provide all the key flight data and should not look foreign to the overall look of the existing panel, but could rather be as if the Falcon got an avionics upgrade package like many aircraft do. I think having them pop up out of the panel at say a 10-15 degree angle could be really cool too. The remaining switches required for a realistic flight would be those that are hardwired to the USB interface controller board mentioned earlier. Things like lights, pitot heat, anti-ice, batteries, generators, fuel pumps, hydraulics, etc. You'd really only need 20 or so physically wired switches at most which is rather easy to do. FSUIPC actually has over 3,000 offsets so it can cover any aircraft ever made.
As for the craft model, flight dynamics and characteristics, you can use any existing flight model which can also be tweaked and fine tuned over time. This is something I've done with a lot of flight simulator aircraft since FS2002. You could actually use anything you want be it a fighter jet or the space shuttle but would of course want to start with something that would give a very similar feel to how you might expect the Falcon to perform.
Luckily there is currently a Millennium Falcon for FSX and while I've yet to install it, it should port fine into Prepar3D.
Other things that you would want to add down the road are navigational aids such as a GPS or FMS / CDU system so that you could program a flight, for example from New York to Tokyo, get airborne, turn on the MCP (autopilot) cruise the Falcon up to the edge of space and land within an hour or two. You can buy a virtual FMS that can be displayed on an iPad too and it will talk with the PC / P3D. There is also other EFB software available for iPad for showing charts, airport diagrams, approach plates, etc... all the things we had to do with paper five years ago.
As for the aspect of space or orbiting, traveling "afar", while you are not going to actually be able to go light speed or to Mars much less Jakku, you would at least get a great feeling of extreme ground speeds, likely over 5,000 MPH and will be able to navigate the entire globe within a very short amount of time. You could also look into interfacing with Orbiter space simulator and perform similar things but because it's open source I can't make claims as to how far you could take it, land on say Saturn for example, interface real gauges, or XML / C+ virtual gauges, etc. I'm sure you can, just that I don't know too much about it and it may or may not prove difficult. Ultimately I want to look into it myself but because I'm a pilot I'm very flight simulator based and P3D is very flexible on all aspects of the design / control interface end.
Anyway, all of this is exactly what I'm currently working on with my Trek Shuttle project, but I just don''t have a blog set up for it yet. Once I get closer I'll post in various forums. I'm just too busy to do all that right now with my regular sim biz and flight schedule.
Lastly, costs. Since you have already built the cockpit you could actually do most everything just as I've laid out for less than $500 but depending on how far down the rabbit hole you wish to go with external visuals you could spend up to $5,000. The added costs will be if you want to have large LCD screens for visuals which should be a minimum of three 50" UHD displays or use one, two or three short throw native HD (1920 x 1080) projectors. Projection ultimately looks the best and is most immersive. UHD would really be the best in both cases but I'm not sure if anyone has made a UHD short throw projector yet that isn't still cost prohibitive (meaning less than $1,500 per projector)
Oh, ...and I also forgot that within the entire process you're probably going to need to learn how to fly. Ok..WILL NEED to learn how to fly.
These links are the basics to get you started.
http://www.prepar3d.com/
http://www.schiratti.com/dowson.html
http://www.leobodnar.com/shop/
https://itunes.apple.com/us/app/virtual-cdu/id634731446?mt=8
http://www.rikoooo.com/en/downloads/viewdownload/8/160
https://www.youtube.com/watch?v=7e0z1znH49Q
IMG_20160125_221050 by Izzy Mel, on Flickr
IMG_20160125_174810 by Izzy Mel, on Flickr
IMG_20160125_174725 by Izzy Mel, on Flickr
IMG_20160204_035333 by Izzy Mel, on Flickr
IMG_20160204_040305 by Izzy Mel, on Flickr
IMG_20160207_200213 by Izzy Mel, on Flickr
IMG_20160207_200436 by Izzy Mel, on Flickr
IMG_20160207_201843 by Izzy Mel, on Flickr
