I had a look today and all the wiring and mounting bracket are there for a stock trunk cd player. I would like to add an aftermarket with mp3 but have a few questions.
1) is there an after market cd that accepts class 2 signal?
2) would an after market work with its own remote?
3) is there a difference in stock head units that allow the rear cd player?

Also I located the amplifier (U80) behind the rear passenger back. No class 2 here in the wiring

Not sure about your questions, but this is the stock player from GM:

thats waaaaaaaay too much for an oem cd changer, thats even expensive for an aftermarket one, if u look around, i bet u could find one for cheaper, as far as hooking it up goes, usually u have to buy the same brand changer as the cd player, but they do make adapters, try nexxon.com thezeb.com or ikesound. com for some deals on the changer and for the adapter, try partsexpress.com

That is really surprising.
When I was first looking by my SSEi back in 2000, there was an identical one that came it before my factory order was ready. They tried to sell it to me but it didn't have the 12 Disc trunk changer. They were more than willing to install one but couldn't because it didn't come with the bracket or wiring harness connection.
So I had to wait two more months for my SSEi to arrive.
There is no difference in stock head units.
Sorry I can't help with your questions.
What is a Class 2 connection???

the means that its a class 2 laser product, it doesnt really have anything to do with ur connections, its just a rating for it, i think its something the FTC has them do but im not sure why

I think it'* the type of connection used between components.

Most OEM changers cost more then aftermarket btw guys. Crutchfield has them a lot higher then that. You may be able to find an aftermarket one that has a remote control, and the deck may be able to be adapted to have input on the cd changer controls, or you could FM modulate it, thru the antenna like most FM modulators do (not broadcasting).

Does anyone own an RF FM CD changer? I was looking into getting one as my stock cd player is crapping out. How is the sound? More specifically, I was looking at the JVC x1500rf 12 disc one.

a friend of my parents bought one for his 93 SSE in 1995 or so, it was a Pioneer 6 Disk FM modulated, sounded excellent hooked up to his Factory Tape deck, its not a bad investment if you dont want to rip out your existing headunit!