It's daunting. I spent a few days reading every post once.
Most of what you need is in the very first post. I made up a quick and dirty list of some additional links when someone needs some help:
For the right-side push button, you'll need to do a Google/eBay/Amazon search for the Switchcraft 201 or 202 push button (either works). They're no longer made, so it's just a roll of the dice to find one.
I was able to acquire production-used sound files for the ringing, pick-up and hang-up sounds. You can download them from my Dropbox here:
https://www.dropbox.com/s/gc4nny1a4ag9n5z/FarnsworthFX.zip
Here's what I use for my main display dome:
http://www.parts123.com/parts123/yb...~S3HB0MDJEQ16614732124q~Z5Z5Z5~Z5Z5Z50000024Q
Some people use these cheaper lab dishes, as well (I prefer the fit of the ford glass, but these definitely work, it just goes a little wider under the faceplate, which can make for a tighter fit of any electronics)
Watch Glass 80mm (3.2in) - Laboratory Glassware, Dessicators - CTechGlass.com
I used a heavily modified off-the-shelf rotary switch from a local place for my build, but I found one that I'm planning on using for my next couple. I've gotten it in and it fits great. You can find it here:
SRBV151102 ALPS | Mouser
And here's a link to my build with a video, if you're interested in seeing how I made up my electronics:
Finally built a Farnsworth (with electronics)
For anything else, you can do a search just in this thread if you're looking for something specific. If you search this thread for "Faceplate" you'll still have quite a few pages if results, but it should be much more manageable. Alternatively, you can look up some of those materials that PeterLC mentioned. Also, some brass ones turn up in the junkyard from time to time.
Hope this helps,
-Shawn