Get an Oasis report, if there hasn't been any major problems then you start dealing. If it's stock and you plan on keeping it stock I'd say buy it. If you keep up with the Maint. on these motors and take care of them they will surprise you. Allot of people will say stud it, EGR delete however I wouldn't do that till you had to... if at all. Now if you plan on tuning it and running the everlovin dogg#ji% out of it then yeah stud it and EGR delete and whatever else. I know when I pulled the Oasis on my 6.0 it only had a couple injectors changed out. But make sure you get a good deal on it. I cussed the 6.0 when I was looking at it and the salesman just sat there. Needless to say I gave allot less than was asked. If the truck is solid, you like it, it has a good price, I'd say get it. Keep the oil changed in it, run some additives to in your fuel to provide lubricicity to the ULSD and enjoy it!
Just my .02 cents.
I just bought a 2003 6.0 with 286,000k on the odo. The truck was solid, clean, and no major issues on the Oasis report. I love this truck!!!!!