Definately call or in my case, I emailed the parts department, and they came back pretty quick. I just told them that I can get the same parts from a gm dealer for 400 bucks, and that if they could do better I would buy local. And they gave em to me for 450, and since shipping for the $400 ones was 80 bucks I feel like I did well. Well as well as you can do buying from the dealer. haha.
I figure it never hurt to ask for a better price. IF they dont go for it, find a better dealer. or order them online or here http://www.gmpartsdirect.com/