I installed the PAC AAI-GM24, everything went smoothly, radio works fine, plugged in my MP3 player and it doesn't play at all.
I followed the intstructions and tried pressing "CD/Aux" once, then twice, then with the MP3 player on, then off...NOTHING!!!
I have the '04 radio with 6 CD changer, which is supposed to work.
And I thought the challenge was getting at the back of the radio (thanks Happy Jack and others for their posts on this, takes patience but a breeze).