If you're making a portable you probably need something to watch it on. (Unless you want to guess what's happening in the game, but I wouldn't advise that) Anyway, this forum is your "Hacking a pocket TV/screen" one-stop solution. Share your experiences and knowledge here.
No, you need the decoder board that comes with the screen. A PSOne screen will work for most portabilizing needs, and it is a great buy too. The decoder board for the PSOne screen is the big round thing.
Yes, but unless you are very good at soldering and finding traces, just cut off the top half. The bottom is not worth it unless you are desperate for a smaller portable (ie, not necessary).