what did you use to convert your component to rgbs? Also what is the default resolution on your OEM screen. I have a mazda and i'm looking to do something similar.
I'm using an Audio Authority 9A65 - it converts component to RGBS (15khz sync) which is what most navigation systems use.. I'm not sure of what the resolution is as I haven't done a CarPC...but I do know that MacPrius uses the same screen, so it should be suitable for a CarPC (with readable text)