Here is my personal experience with my 08 6.4. Bought new, and kept it until last year when the 5 year hundred thousand mile warranty ran out. It had 27,000 miles at that time. I got rid of it because the cab had to come off twice for engine repair, I had two injectors replaced, each at different times, a radiator, rear main seal and bedplate and lastly several software updates to attempt to make it quit smoking during regen. All replaced under warranty. I couldn't afford to keep it without warranty so I traded it for a Cummins.
Expect the fuel mileage to be atrocious. Pulling our old camper with it which only weighed about 7000 lbs I was getting 7.5 to 8.5 mpg and averaged 11 empty. When it was running it ran good and had tons of power. I say save the headache and get a Cheverolet or Ram.