My experience with 3rd gens:
Injectors will be a problem at some point on any of the 5.9s. Depending on how bad it is, you'll get a hard start or no start with white smoke at idle and the truck will make oil. (replaced mine at 118k)
Plan on front end work between 150k - 200k (ball joints, hubs, steering), I believe it was around 150k on mine
Auto trans will need rebuilt usually before 200k (mile was 130k if I remember correctly)
Dash will crack at any given time, I ordered a replacement dash from LMC
Wiring for locks and windows will have issues, usually its a pinched wire where it passes in to the door, pretty easy fix.
03-05 have tail light circuit board issues that cause a "lamp out" chime/alarm to constantly go off, put dielectric grease on all connections of the new boards to make them last longer
4th gens are much nicer in my opinion and a 2010 wouldn't have a DPF, but I switched to Ford and have had much better luck with the 6.7 powerstroke