Welcome... Since I have a similar truck, I'll share my experience
I've had my 2011 Denali for 2 years now. Got it with 180,000, now has 200,000; alot of them towing a car hauler. I paid less knowing it was high mileage but fairly well maintained and figured I spend some money on it. So far...
A/C blockoff as rear AC lines were corroded thru
left motor mount
broken exhaust studs fixed with Kral gadgets
Oil leaks under Vlom/Intake/ oil pressure sensor
DOD disable plug-in
failed torque converter resulting in required trans rebuild
new rear suspension compressor and shocks
So, its done it job and total spent is about $22,000. Not sure it works out or I should have bought a $22,000 truck to start with.
Maybe most of these things are regular problems that either have been addressed or will need it.