[Christ]

as far as having another monitor, most laptops have a secondary output... remove the primary monitor, after setting the computer up to display to an external monitor, then connect a VGABox (google: VGA BOX) to the computer, and you can use a standard RCA jack after that, which means that any in-car DVD player will accept the signal. It's basically converting the signal from computer-ese to NTSC (or PAL) that will be the hardest part.

BTW, if you only want in-car MP3, you can do it w/o a head unit.. you just need an amp and a equalizer...