I agree with Transamz9 they are motors that normally need good attention and maintenance. I also think the price is too high for the miles plus the fact the dealership has it on lot to sell yet the battery had to be jumped after 4 days. Makes me wonder how much attention they paid to recondition truck.
I currently drive one that I bought with high miles and had to spend the $$$ to get it running right but it (engine) hasn't given me any problems in the 2 years I've had it. I have been basically addressing other parts that wear out like others said like power options that stop working and suspension/brakes wearing out. In the meanwhile I bought another as project, fixed it up (with parts from another 6.0L) and sold it with only FICM replacement.
As other says there are other choices some with more stellar backgrounds but if this is what you want make sure you go into it with your eyes (and possibly wallet) open.