Here is a good place to start:
What to look for when buying a used 6.0L
Things to consider about owning a 6.0L
Probably the single most important thing you could do when checking out a 6.0 is to have an electronic gauge set with you. They plug right into the OBD port and can access many of the stock sensors. The cheapest way to do that would be the purchase of a scangauge2 available at most auto parts stores.
Once you have that, and plug it in, you want to access the engine oil temp and the engine coolant temp. Then, take the truck on a test drive, watch the coolant temp and when it reaches 190°F (give or take a few degrees), take it out on the highway. Find the flattest section you can, set the cruise to 65MPH, and once the engine oil temp levels off, compare it to the engine coolant temp. The temperature differential will tell you the condition of the oil cooler. Should this temperature spread (AKA: delta) be 15°F or more, the oil cooler is plugged. As part of that repair, the egr cooler would also have to be replaced. Higher than this could mean that the egr cooler has already failed too. Keep a close eye out for the telltale white smoke. You will see it coming to a stop or accelerating from a stop. If you fall in love with the truck, but see these issues, you could use that as leverage for a better deal. The repair of those will run right around $12-1500. BUT, also be forewarned that those failures CAN (and do) end with blown head gaskets. So, actually thinking about it more, you see that white smoke, walk away...
I have seen a few new 6.0 owners that basically bought someone else's problem by not knowing what to check. Don't be the next one...
That being said, 110,000 miles is barely broken in if it is properly maintained.