With respect to hood alignment issues, I have a 2011 Convertible in which I could not close the hood when I brought it home after delivery. After adjusting the rubber inserts I managed to get it closed. Took it to my local Chevy who supposedly fixed the problem. Asked what they dis, move the catch forward. About 3 weeks later the same problem occurred, but I managed to fine the right high and location in which the hood would close. The issue I later encountered at my local tire dealership was that they all wanted to open the hood to look at the power plant but were unable to close the hood. Note this dealership in North Scottsdale is one of the most inept concerns I had the displeasure to deal with (couldn't resolve CEL after 4 visits)
After examining the hood I noticed that when it was closed the problem area (passenger side) was siting lower below the fender than the driver side. Major clue which the dealership and there mechanics (I'm being nice here), couldn't notice or just didn't care. In light of the aforementioned, and with this clue I loosen the 3 nuts and move the catch up so it would engage correctly. The procedure resulted in a hood which can easily be closed by anyone, even the service advisers at the dealership which I will never again frequent. Unfortunately, GMC or these bogus dealers haven't taken the time and made the investment to train their personnel. Customer satisfaction is a thing in the past.