Hi I have a F250 6.0 with 90000 miles on it.  At  70000 I did the minor bullet proofing.  Same as you I never had a problem was just concerned.  Since that time the 20000 have been heavy haulin all and over
 the mountains at least four times, we live out west.  I love my truck it is in great shape and it runs great.
Look for a diesel specialist in your area and go see him and ask his advice.  I have heard that if the engine hasn't gone bad by a certain mileage it should be good to go.  I do all other maintenance myself.  Compare what someone will give you for your truck then what a new one will cost.  Like others have said Most people will low ball you on the truck because its a 6.0.  Peace of mind may not be cheap but new does not always mean better.  Good luck in whatever you decide.