Well you cant just say Gm, It happens at Dodge, Ford, some shops are outragous like that. Its no wonder people are buying into Imports.
I deffinatly would not hav them work on it!
Like GTP Dad said 600-800$, thats about what it should take.
My wife bought our GA SE from a dealer(after I told her not to) and when the Radiator burst they had to Order one, 2days, then they said the water pump 'looked' bad but never changed it. Next week the WP went out and it was another 2days before they got the parts. This continued for 2 years before we had enough.
It was ridiculous , accually took them to court and got all the warnty money back, and a little extra for our wasted time and effort.
I had all sorts of evidence though, vids of what I KNEW was wrong, then they f*** with something else(loosen bolts), cut the CV joint boot clamp so it leaked grease everywhere.
GLad you got it fixed man!