If you find a worthy diesel truck, you might want to spend $100 at a shop and have them hook it up to a laptop (not a code dumper) and have them drive it. I had Douglas County Diesel do this to my 7.3 Ford and I did learn a few things. I wasn't entirely happy with the inspection (for instance - they should have looked at the turbo fins for dusting), but I learned that the truck was basically sound.
A buddy of mine just got an '05 Cummins Dodge and a number of pricey body and electronics stuff promptly failed. He's a Toyota guy and isn't real hot on Chrysler quality at this point. The engine has been fine, however.
Colo Springs, CO
'78 FJ40, '89 FJ62, '98 4Runner