I love my 7.3 diesel. I have no problems finding fuel. ( just traveled from MN to MA to MN to PA to MN) I do put in premium for a couple pennies more when I find it or a fuel additive to protect my investment. It is all Ford/Motorcraft components. I change the oil and filter every 5k and fuel filter every 15k. I maintain the tranny and coolant per the mfg recommendation. Personally, if you cannot get proof that the 6.0 has been "bullet proofed" I would stay away from it. Try searching with www.searchtempest.com to expand your search.
I will not go back to gas. I get 11 mpg with the camper and 17 to 24 without it. It has 225000 miles on it. I love the smell of diesel in the morning!