Thanks.I just installed BlueStar in place of OnStar & had to remove the rear seat to access the space under the rear window. The bottom rear seat can be pulled out by 1st pulling rear by seat belts & then by front. That will allow you to see the 4 bolts holding the bottom of the seat back. There are also 4 nuts to be removed from the trunk to release the top of the seat back. Can be done in 1/2 hour or less if you know how to get the seat bottom out (the correct angles...). It should be an easy change, as I would think not a total change of car.
Hope that helps. You can also search for the BlueStar as there are some photos for those of us who need to add BlueTooth to our rides.