My first comment is that's a small bedroom for full timing. Very little room for hanging clothes, so it would be a problem for my DW.
Since this is smaller than most full timers fivers, I recommend you get the F350 in case you want to upgrade to something larger if you love the lifestyle. If you plan to travel a lot and mostly in the western states, then go with the diesel. If you plan to stay in one place a while and put less than 10-12K miles a year on it, then consider gas. If you go with the 6.2 gas, I would seriously suggest you bypass the 3.73 rear end and go to the 4.30. It would then be equipped to tow 15K lbs. Given the fiver is small, I would also suggest you get the long bed truck for extra storage.
Most of the other stuff is personal preference as far as trim levels and options. Enjoy and have fun.