an lcd screen that is at the MINIMUM 12 bit will give you decent picture for dvd... 18-bit would be even better.
size is what counts for viewing computer screens... if you have a 5 inch monitor think about the resolution you are going to have to run to get viewable text. i wouldnt go for anything under 8.4 inch. but that is a personal opinion...other may tell you that you can go smaller for a lcd screen.
also, make sure you can run at least 640x480 on the resolution. you might not want to run it to high, but at least you have the option to do so.
VGA lcd screens are the way to go if you want clear outputs. composite video is decent for something like a playstation, but for computer video... vga is the ideal solution... especially since you have a video card outputing vga as a default.