Hi Rondall!
Welcome to the RPF!....That said...run away now. I'm serious, run and run FAST! You have no idea the Rabbit hole you just fell down! Building this stuff is a worse addiction then crack.
Now, on to your build! :lol
I thought there was a tut around here someplace that had all this, oh well, I'm board and have some time (fiberglass is setting up on a prop right now :lol )
1st. See if someone has made what you want already. If so, they will be a fountain of info for you....or not. Heck, try tracking down where the REAL screen used prop ended up. This does a few things for you: Might find it and be able to actually get IT, or maybe some decent pictures (thats 2nd) AND you'll learn a lot of the history of the piece. Something us collectors enjoy "Yeah this E-11 Stormtrooper Blaster was the one used by the guy who got Jedi Mind Tricked!"
2nd. get pictures, lots and lots of pictures, the better the pictures, as in high res, the better your understanding of what your going to make. One picture especialy look for, one with a known object in it next to the piece. This can be like finding the Rosetta Stone to unlocking the size and measurements of what your going to build.
3rd. Decide how close you want to get. Like your Dr.Theo as an example: You want the "look" but on a budget, a simple 12" clock, some LEDs, a printed picture put on the "face" for the circits, done.
Better: Machined pieces, hunt for the exact lights used in the original, use a real circitboard, voice box, memmory chip, motion sensors so he talks to people as they walk by...
That help?