Be mindful that most shops -especially dealers with high overhead- try to charge all they can.
Case in point: I went to my nearest dealer and quoted a replacement transmission with the parts guys. MSRP 2500 and my price 1900. I was considering having it installed at an independent shop.
In the end I decided to have the dealer do the labor also. Well, what do you know, when I took it in the service department priced me $2500 for the trans, plus the labor! Of course I told them that was not going to work, so after some background consultation they agreed to honor the previous quote. Caveat Emptor.
Point is be an informed consumer, and you’re in the right place here.
GM parts online shows MSRP 1600 and selling price of 1000 for front diffs.