it's really not at all a hard thing to do, however if you're here asking where to begin then odds are you would benefit from a little help, rather than attempting it on your own.
you should get the best combo of knowledge and economy by just going to a home stereo/theatre (gag, but fine for this) store and telling them what you want to accomplish. basically you need a couple VERY simple audio/video switchers, the right cables to feed each signal source, and some long runs of cable to cover the distance to each screen.
it'll be really easy to design and build this on a tabletop and then just add the long runs of cable inside the walls after you've determined what plugs into what.