I know this is an older post, but I had both replaced.
The reason I came back to this is because I got a letter in the mail from GMC about being reimbursed for this repair. Luckily I kept my dealer receipt on this and I have mailed it in for the reimbursement. The total price I paid for the labor and parts was just under $400.
I'll update again if/when they send me a check. It was a pleasant surprise actually. I guess I'll see if they follow through.