Insurance companies tend to offer their "lifetime" warranty on collision repairs performed by their preferred providers. If the dealership was one of their preferred providers, then yes, the insurance company should handle it.
If the OP decided not to utilize one of the insurance company's preferred providers, then he's on his own.
There are some questions though:
1) Is the dealership a GM-certified collision repair center?
if no, then 2) did the dealership outsource the repairs to a GM certified repair center? If the outsourced collision place is not a GM certified collision repair center... probably best to call up GM customer service and open a case file and get corporate involved.
