Look for a pinout for the screen. If not, look at the circuit board. Sometimes it says flax like "composite in" and "S-Video in" or "audio in" on the board itself.
About half the time, you have to keep the whole DVD player in order for the screen to function properly. If it doesn't work, then there's really nothing you can salvage from it.
I do have the rest of the DVD player, I'm not sure what works or what doesn't, but before I took it apart the disc wouldn't spin, however the screen flickered.