I have done this in my 07 Grand Prix GT with the monsoon.
Precision Interface Electronics GM12-AUXv2 Connect a portable music player, satellite radio tuner, or DVD player to your factory GM receiver at Crutchfield.com
Plug in and play. You'll need to tap into the power (thicker yellow cable from the connector from inside of the car) and then get a RCA to Aux so you can play your tunes.
Hope that helps,
-Garrett