AFAIK all the G6 stereos will fit with the same connections (except 2009.5+) It's just the different options in the radio that differentiate the RPO code. I believe any can be programmed to match the VIN of the car. I haven't done any stock installs at all so I can't say for sure...
You can check if you have the Monsoon amp in the trunk to determine if your system at least had that.
It's possible someone removed the amp, or replaced it, or just went with the head unit replacement, but if the amp did once exist then you should find wiring for it.
One option available is to swap in the Speedometer cluster and cruise control/DIC switch assembly from a 2009.5-2010 G6. The cluster houses the DIC and the switch allows you to control the DIC.
http://www.g6ownersclub.com/forum/203-how/26074-2010-speedometer-swap-how.html
You can check if you have the Monsoon amp in the trunk to determine if your system at least had that.
It's possible someone removed the amp, or replaced it, or just went with the head unit replacement, but if the amp did once exist then you should find wiring for it.
One option available is to swap in the Speedometer cluster and cruise control/DIC switch assembly from a 2009.5-2010 G6. The cluster houses the DIC and the switch allows you to control the DIC.
http://www.g6ownersclub.com/forum/203-how/26074-2010-speedometer-swap-how.html
