Ok, I bet everyone that wants to replace their Bose headunit with an aftermarket headunit can't find the info. So I'll try to help from all the stuff I found.
Here's a site shows how to remove the headunit, speakers, CDM, and antenna. http://www.carstereohelp.com/strcadillac.htm
Here's the one for the wiring harness for Bose systems. http://www.installer.com/wires/
I'm attaching 2 pictures which makes one diagram.
If you don't get the wiring harness to by pass the bose system and the amps, you'll have to rewire the whole system. Meaning new headunit and new speakers all around.
I didn't use the by pass harness. I used the Battery, Ignition, and Ground for the CDM(reciever in the trunk) then wired them to 3 wires going to the orginal Bose headunit. I hooked those 3 wires up and the new aftermarket headunit worked. (It came on, worked, and retained memory of settings on the headunit after the car was turned off.)
Diagram is for a 1995 Seville.
Hope this helps everyone, if not someone.
(This should be a Sticky or FAQ)