research showed that how bigger your screen is (in resolution like 1920 by 1200, that's really big, on 17 inch or 1024 by 800 on 30", then is de 17" better) the more productive/faster you are. So I'd say (which I did) go for the biggest screen. Your macbook pro has a mini DVI connector. It's specially from apple. So you need to buy a mini DVI to VGA connector (I guess it's 30 dollars from the apple store). Only when you have a really big screen you need mini DVI to DVI. But you'll probably can ask what the connection is (try google for pictures). For the rest it's just plug and play.