In theory it might be possible if you could find out which wires are for video input. Then you need to figure out what type of signal it accepts (composite, RGB, etc.).
I guess if no one else has found out, or if you can't find any usefu documentation about it, you could try looking at the back of your unit.
If you're a bit hesitant about mucking around with your own system, perhaps visit the wreckers and buy the same unit as yours. Then you can muck around with that one.