I have a 2007 new body style 2500 with the factory install CD/GPS-Nav radio. As an FYI - it did not come with XM installed.
My wife has the XM Mini-Tuner installed in her car. This is a nice unit because you can "pull" the XM reciever from the XM Mini-Tuner in that car & plug the reciver into another XM Mini-Tuner in another car (or Chevy truck in my case).
Here's a link to the XM radio:
XM For the Car and Home
Does anyone know if the factory OEM radio is "plug-n-play" compatible for this kind of XM unit?