I specifically searched out this vehicle. Needed a dependable, naturally aspirated diesel, 4x4, with some good cargo capacity, but without towing capacity. As soon as I bought this truck, I installed a 4" lift kit, 35" all terrain tires, and then went hunting.
Lots of people dislike the GM 6.2, but I've had few problems. I suspect that the rest of the drivetrain is weaker than the engine. Only 140 hp though, so it can be a (sick) dog on hills. I get pretty good fuel economy, once having gotten 25 mpg, though it was a concerted effort. I suspect that I regularly get 18 mpg. I usually drive in "D", but when I get on the freeway, I'll shift to "OD". Road noise at 80mph is hardly noticeable. Big tires make for a bouncy ride at slow speed, but always within control.
Tune ups? Change the oil, filter, and wiper blades.
Replacement parts can be high for diesels. I find that it's best to buy Delco parts, as some aftermarket manufactured parts are inferior; glow system parts in particular. If my current glow controller goes out again while I own this truck, I will save my money, and just wire up a momentary switch to actuate the glow system. Without the glow system working properly, (long enough duration and repeated cycles), the diesel is a bear to start when cold (<40f).
The 6.2na engine in this truck will drive through a thermo nuclear pulse without stuttering. Everything is mechanical. No computer.
This is a non catalytic engine, meaning that it has minimal necessary pollution controls.
There are many ways to improve the performance of these engines, from non-egr intake manifolds, to headers, to turbos. Lots of resources on the internet.
I'm looking to get rid of this truck soon, as I now find a need for a tow vehicle. If it existed, I would buy a civilian 1 1/4 ton Chevy truck of the same vintage, with a Banks turbo, 5 speed manual, and AC. Unfortunately, such a vehicle does not exist, so I will probably get a Ford F350 standard cab 4x4, with a 7.3na diesel and a 5 speed.