sounds like fun... I know someone else that put a PC in his car with a small LCD screen for titles and song info... he used it strictly for MP3's.
I'd like something like that, but I dont have the $$ now... plus I only have a dial-up connection at home, so dling songs is a pain. In the future when we upgrade to cable or something i'll probably do a car-puter, and run a wireless network to my house, so when my car is parked outside I can DL songs straight to the car-puter, or easily transfer from home pc to car.
good luck with the project! I'd really like to see some pics when its done!