There is a Delco radio service manual available. I haven't seen one, but repair shops should know where to get them. I've used the Sam's documents many times for other projects, and they are the best.

If you want to use a CD changer, you will either have to convert your original, or use Secret Audio or something. I chose to install a Pioneer MP3 player instead, in the underdash position. It was a lot cheaper, and would interface with a changer if I wanted to install one.

I can help you with the speaker level outputs. Dark blue goes to right rear. Brown goes to left rear. Black with purple goes to right front. Tan goes to left front. Other wires on the radio connector are yellow (power), gray (light from dimmer).

The other lead on the amplifier connects to the underdash rear speaker harness adapter. I'm not sure what its function is.