Here's a dirty little secret about scheduling appointments with the dealerships. They're BULL***T. Your truck goes into the back of the line when it shows up. The vehicle that shows up after you is placed behind yours. First come, first serve. We're use to the opposite because of other businesses like the dentist and doctors offices. They'll get to your truck when they get to it in the order it arrived. I'm in the exact same boat right now. My truck is in for minor warranty work. They won't approve a loaner until the tech looks at the truck and confirms warranty work. That should take 2 minutes, max. It's a failing bushing on the tailgate, and an led fog light with a short. I'm without a vehicle for maybe 1-2 weeks, based on what I've been told for 2 simple jobs that should take 15 minutes max for both jobs combined. The only reason I would get a loaner is because they have to wait for the replacement parts to arrive.
If it sounds like I'm pissed off at the dealer or GM, understand that I'm not. It's just the way things are right now. I have no doubt the techs are doing their best, and the service writers that have to deal with dumb a**holes like you and me are burned out at the end of the day because we're up in their business being as displeasing as we can be (Actually it's you, not me. I'm nice to people when things go south because you attract more flies with honey than you do vinegar.). My truck is my daily driver. Being without it affects everything I do. The only thing that could've prevented my inconvenience is doing the work myself, even though it's covered under warranty (would've cost me about $200 and 15 minutes). I made the choice I made, and you made the choice you made. Man up and deal with it.