Ford diesel pickups had lots of problems that continued through the 2010 model year. After that they have been a lot more reliable and this includes the engine and its components and the transmission and other aspects of the truck. The engines in the earlier trucks got all the attention but these trucks had lots of other problems are best avoided. Some people were lucky and had no problems but many people were not lucky.
Check Edmunds and Kelly Blue Book for the price. Problem I found when looking for a used diesel truck was that all the owners paid way too much when they bought them new. Most still owed $35,000 on a 3 year old truck. I gave up trying to find a used one at a reasonable price and instead bought a new diesel pickup truck fully loaded for under $42,000. This is a good time to look for a new 2014 sitting on a dealer's lot and a local dealer can check in their computer and find all the 2014 trucks within 500 miles and do a trade to get it for you.