if you want to display regular composite video like you get from a vcr or dvd player, you should get a display that is designed as an in-car display for vcr or dvd or game machine.
the dstn display on the i-o is not bright enough to be seen well in daylight.
the i-o display changes slowly when there is anything on the display that is moving. even as a computer screen, with Windows it is like having mouse trails turned on.
the i-o display needs a display controller chip like the trident chip in the i-o, and probably a cpu to run that.
if you live in a big city where there are stores that sell and install in-car entertainment systems, check out what they sell. i have seen 7" 12volt, composite video tft displays for in-dash or seatback installation for about $100.
trying to convert the i-o display will cost you more for parts, time and hastle than it is worth (including the value of an i-o without a display).