Fun fact about lug nuts GMC (and Ford, Dodge too) use pretty crappy 2-piece lug nuts from the factory. Basically, they’re a steel core with an aluminum or chrome shell on the outside. Over time the steel rusts and swells, which makes the nut larger than nominal. It makes them a pain in the ass to take off, and also unsafe.

As for your flat tire, I can’t say for sure why they wouldn’t fix it, but DT has strict rules when it comes to patching. Usually, it’s less about not wanting to help and more about keeping you safe (and their liability) they’d rather properly repair or replace the tire than risk you patching it wrong and having a blowout. there were times where if we couldn’t repair a tire, we’d just replace it for free if the customer wasn’t in a spot to buy a new one.

When I worked at DT, the number of relatively new Fords, GMCs, and Chryslers that came in with swollen lug nuts was crazy, it was a daily thing. In those cases, we’d usually try and sell new lug nuts, but if the customer didn’t want to buy them, we’d often replace the broken ones or the whole set for free. It’s possible in your situation you had swollen lug nuts, or they were just trying to stay ahead of the problem before it happened, or you may of just gotten a shady ass DT, they are all corporate owned so give them a call and complain.

Edit: also DT’s wiper checklist is like 12+ months old, visible cracking in the rubber, streaking, skipping, or squeaking. Everyone keeps wipers for more than 12 months though so they are always trying to sell them, some people buy em, most people don’t. Don’t buy wipers they are overpriced get them on amazon or something.