If you drop in a 2009 head unit, will that add bluetooth functionality/phone connectivity to the car, or are there other things that will need to be switched out as well? Thanks!

They told me that the bluetooth is in the OnStar box, and that they will not sell you a box not matched to the VIN.

I tried before I finally broke down after a year and had the Kenwood installed.

Plus the new head unit is over $4000 new (best price I could get, my dad is retired GM). It was cheaper for me to install the Kenwood and it has so many other advantages that I think it was the best choice.