It will do the job, just not very fast so don't be in a hurry. As for mileage it depends on what trans, gears, tire size, and how you drive it. As an example if the truck has a turbo 400, 4:10 gears with 33" tires seeing mileage in the mid to upper teens wouldn't be hard, if you drove like a sane person though. They can last a long time just need to be maintained properly. The 6.2 does have some little quirks but any engine does, just a matter of learning them.
If you're going to be towing often or kinda heavy I highly recommend getting an egt gauge. Plus remember that a 6.2 WILL NOT tow as fast as a modern diesel so don't try to drive it like one or you'll blow it up.
