If you change the belt, throw the old one under the seat as a spare, and take a 1/2 inch drive breaker bar to change it. If you decide to throw new coolant hoses on it, get the upper one for a truck with dual alternators, because that will go around the belt, not through it, making it possible to change the belt roadside, without having to open the cooling system.
Maybe throw a new air filter at it, if it's getting pretty dirty. Mostly for mileage
I'd jack the front end up and check your ball joints and steering linkages for play. Also check the wheel bearings, spin them, too. I know I had one that was starting to get a couple tight spots awhile back.
As far as the tires go, I'd go with whichever ones give you better mileage, 2000 miles, that adds up quick, especially with 4 dollar diesel. But, your summer rims do look pretty badass
2001 F250, 7.3, Automatic, 4x4, 33's, Leveled, Cobra 29 CB Radio, Single Firestick anteanna, Pioneer Head Unit, Riffraff 6637 Intake Kit, 4" turbo-back straight pipe, Dual Alternator Upper Radiator Hose, AutoMeter Boost, Pyro, Trans Temp, Delta Toolbox, Gooseneck Hitch and a heavy right footed driver...
Wishlist: 160cc single shots, GT38r, BTS, SRP 1.1
REAL TRUCKS DON'T NEED SPARKPLUGS!!
Lord, please take care of this drivin' fool...