GM radio's question...
 

Which GM radios hook up with the factory 12 disc changer?

All tape decks out of 93-02 Firebirds/Camaros for sure. 2000 and up Firebird CD decks too. Not sure about Camaros.

How do you control the cd changer from the radio (enable it and control it)

It is also compatible with 2000-up Camaro Monsoons. Assuming it is connected, and has CD's loaded, the TAPE/AUX (or CD/AUX if you have a 2000-up CD unit) button activates it when you press it a second time. Can't remember what buttons on the radio itself do what, but for the steering wheel controls, pushing "PLAY" does the same thing as the TAPE/AUX button. You can use "SEEK", up & down, to change tracks on the current CD. You can use "PRESET" to change to the next CD in the changer.