Question about the GTP radio

So there's this button that says CD/AUX. I have an MP3 player that I would really like to plug directly into the back of the radio. Does anyone know if there is an AUX input port on the back of the radio? I'm really tired of using an fm transmitter and I don't want to spend $600 to replace the entire radio system.

what year is the GTP? i'm not sure about the '04 up models...but the '97-'03 does not have an aux jack in the back of the radio. that button on my GT controls the 12 disc changer.

Unless you are just bent on keeping the factory cd player, I would change it out. Sure you would have to get an interface to use the steering wheel controls for it, but its a better decision. Sound quality is much better out of an aftermarket. Face it a grand prix is not a cadillac or something else with a high line stereo. If you have a Bose its worth keeping but not the standard. As for the mp3, aftermarket units have a usb port on some of them. Mine has it and I never touch the mp3 player. It pulls the memory from it and displays it on to the screen. I can also hook up a memory stick to it since I don't actually use the unit. The headphone jack inputs don't have the best sound quality and don't have a clean look to them. They also require you to use the mp3 player and then use your cd player so that defeats the purpose in my opinion.