If you are looking at ford, then you have a few options. The 7.3L is the best powerstroke they ever made. If you can find one thats an early 2000's with not many miles on it, you will be doing great. The other diesel option in those years is the 6.0L. The first two production years of it sucked, but the 06's had significantly less problems. With a ford, both manual and automatic trannies are decent. i've done a lot of research on all these, I had a 7.3 for a while and loved it, but when I went overseas I couldn't see keeping it when someone else can use her.
I've also had a cummins, which IMO is pretty much the best diesel you can get, I had it in a FORD LOL. It was a HS project, and it was awesome. Only problem, dodge's tranny's suck, and if you put a juice box on them they have a tendency of the injector pump going. As far as Chevy's, well they are Chevy's LOL. I dont have anything bad to say about them really. All the trucks/companies have their problems. But do you need a diesel? What will you be hauling? And I see you are from PA, check these guys out. http://www.autotrader.com/dealers/dd...countryent.com
They are up towards scranton, off I-81 a little ways. They usually get some decent stuff in there, and they are pretty knowledgable if you have questions.
2008 700xx; Power Bomb header with power core 4 exhaust, Power Programmer III, pro armor nerfs, prm products control front and rear bumpers and full skid, 10" ITP rears, ITP Baja's fronts, RZR 2's all the way around, Uni filter, 13t sprocket, CCP steering Damper, DS450 shock swap, Dual Gasser Throttle, bar risers and Moose barkBusters. 730XX kit plus other engine mods!