OP, if you want a new fender where the holes are in a different position by 2mm you'll need to make it yourself. Having it repaired via warranty will not fix the problem. The new fender will come from the same assembly line where your original fender was stamped. "Man Card" holders also recognize this. The self-described men will roll up their sleeves and fix the issue, such as removal of parts, sanding to bare metal, filling hole, making new hole in correct location, priming, painting, clearing, and reinstalling everything. There's probably a few more steps involved, but I think I made the message clear. Is it really worth it to you to do all that for less than 1/12 of an inch? If so, feel free to write up a tutorial so others can see your work. Include pictures. Everybody on the internet loves pictures.
Btw, there's a good possibility you missed an even more obvious manufacturing snafu. Do the body lines between the cab and bed line up on the driver side? This is one GM actually has a fix for via the dealership installing shims.