re. Stereo
One thing I can tell you is the old 9v battery trick. You can use it to find out wich speaker you are trying to find by touching two wires at a time to the terminals. Kind of a hit/miss way but I watched them do it a Good Guys and thats the only way they could find what went to what. Well, first find the ground, then the Batt, then the ign. and finally the 9v to the speaker trick.
But I swear to Jeff....take it to Good Guys and pay 'em fifty bucks. They will do a half-install (just head unit) and be done in 20-30 minutes. It saves you sooo much time.
I swapped out my entire sound system about three months ago. They quoted me like $250 and $45 per speaker, the extra $45 per was because they needed to rewire the whole car. I ended up doing it my self and it took me at LEAST 8 hours. More like 12 with the beer breaks in between.
I ended up with 1 MTX 5 channel amp, 2 Polk 6X9s in the back (with custom made grills, I had to modify the exsisting ones for clearence), 2 Boston Acoustics 4X6s in dash, two JL Audio 4 1/4s (or something like that) in the doors, 2 JL Audio 8" subs in the back and a Pioneer Premiere CD/MP3 player w/5channel 5volt outs.
Sounds killer but 12 hours!! Some things are best left to professionals.