I base my reply on personal experience with my 2014 335ss. By now you should have a list of things you want recitfied - start there. I also included things I wanted confirmed and verified correct - such as wheel bearings, axle "truness" (no flattening), brakes, A/C and Heating ducts (check hidden connections), slide operation and gasket material, etc. Basically, I read this site on a daily basis and look for things that have bugged other owners - usually a good place to start. Even if you are not having a problem, asking them to verify and confirm "correct" operation is a bit of insurance. Because, according to a nephew who used to work Customr Service, the request is "on the books" in case you have a later issue.....
Roselyn and Darrell
2007.5 Silverado LT/EFI Live Tuned Duramax/6Spd Allison/Banks Ram Air with Super Scoop/Edge CTS Gauges/Air Lift Load Lifter 5000 Ultimate Air Springs
2014 335ss Cruiser Provincial