**EDIT** As far as the 6 disc MP3 units go, I checked the a/v forum. Looks like I need a RF unit specifically from a King Cab frontier, because it has an internal amp. The Crew Cab models have an external amp so it won't work properly in a truck like mine with a single disc deal. Soooo, sorry steve500, would really like to, but can't do it.
Any king cab owners have a mp3 capable cdplayer laying around?