I just bought an '06 F350 with a V10 gas engine after a LOT of research on the pros and cons of a Diesel. There are several things to consider when you make the jump:
New, a Diesel is about $6800 more, used $3-5000
Fuel mileage - the older ones were better - before pollution controls got so tight. Diesel wins here by 2-3 mpg. Fuel oil vs gasoline where I live is only ten to fifteen cents a gallon difference. You need to drive a LOT of miles to make up that $6800 difference
Maintenance - 15 quarts of oil (Mobil 1 is about $5/qt - and you want that for the extra MPG), an oil filter is $25, a fuel filter is $60 vs 7 qts of oil, $4 oil filter and a $10 fuel filter. Then you have 2ea 900 cold starting amp (very expensive) #27 series batteries.
Stop and go driving will drive you nuts with Diesel engine "rattle" - and it increases the maintenance factor by some amount - my guess is 2X. Most of my driving is local.
Pulling a trailer - how big is it and will it be pulled highway miles a lot - if so, then Diesel may be a good investment.
Trade in value - in 2-3 years it will be pretty good, beyond that, well, they seem to drop like a rock, just like a gas truck.
Engine longevity - the rest of the truck will wear out before either engine but a well maintained Diesel does have an edge.
Pucker value - hands down Diesel.