Help on OEM Head Unit in 2007 Chevy Impala LS

Hi. I'm a new user on this forum.

I'm scratching my head on how to approach this. I own a 2007 Chevy Impala LS and am interested in replacing the radio with either the XM-ready head unit or a GPS-navigation unit.

Currently, my car is equipped with the basic AM/FM/CD head unit and OnStar with an active subscription (no Bose equipment). For XM, I have a Delphi Roady 2 unit attached to one of the vents. I prefer having everything built in to the radio to cut down on the clutter on the dash. But, I would prefer OEM instead of aftermarket if possible.

I originally looked into getting the XM-ready unit (like the ones in the LT, LTZ or SS models). I saw one on eBay that was pulled from a 2006 Impala that I'm interested in. Guy says that it is only a matter of putting it in and reprogramming it to my vehicle. If I get this receiver, would I also need to get the tuner and antenna to enable XM functionality?

The other option is the GPS navigation unit. I saw one on ebay (GM OEM Factory Navigation System GM Part # 15942542). Can this work in the Impala and, if so, how difficult is it to get it to work? I read on other forums that it should work, with picture proof of it installed in an Impala. If this works, I would prefer this option.

Thanks!