Found a 2006 F250 Diesel, looking to purchase

I found a 2006 diesel that I have test drove and inspected. The guy used the truck occasionally and it only has 35,000 original miles. He took great care of it body wise, not a single spot of rust or paint fade, etc. He told me what he did engine wise, always used amsoil, always changed fuel filters at 10k, always ran fuel additive, etc etc. So I asked a couple friends and some are telling me the 6.0's are nightmares. I've searched and searched and read some of the horror stories, but should I be concerned with this truck and the sitting it has done? It has around 1300 hr's on the engine. I know in the gas world sitting can be one of the worst things you do to a car. Any opinions before I make this purchase would be appreciated.