Welcome,
I have an 03 6.0 and love it. Like said above, take care of it and it will take care of you. Proper Routine Maintenance is a MUST. I go 5000 on oil and oil filter, and 10,000 on fuel filters. Use ONLY RACOR, IH (Navistar) or Motorcraft filters and a Hi Quality Full Synthetic Oil. Currently I am running a set of Fleetguard filters (Cummins) but personally verified by the markings on the filters they are indeed the exact same as OEM... (IH and Motorcraft and these Fleetguards are made by RACOR). and use Chevron DELO 5w-50 Full Synthetic Oil. Also, I highly recommend NO TUNERS!!!! I don't run one, and in 100,000 miles and 8+ years I haven't felt the need for one. I am in the same boat as many above and still have the factory head gaskets, turbo other "you will have to replace" (as professed in other places) and just rolled over 154,000 miles. I do recommend, if you live in a place that you can "get by with it" (no emissions testing) to do an EGR Delete. I did one on mine, because one of the external supply hose leak, my cooler DID NOT FAIL. This one change has taken so much unnecessary heat out of the cooling system it's amazing.....
Show the truck some love, and it will treat you right...... DON'T SKIMP ON MAINTENANCE!!!!