RE: Rear Differential Oil Change?
Everything I've ever worked on, HMMWV, 7-ton, 5-ton, LVS, Skytrak MMV, John Deere Tram, Case 1150/1155, Cat D7, D8 620B, all have a recommended change interval for anything with gears, Differential, Final Drives, and Hubs, and with the exception of the 7-ton truck, everything in the Marine Corps is close to as old as me, even the Brand New gear is almost a decade old, and everything still runs fine. I don't care how long someone has been a mechanic it doesn't mean they know a damn thing, I've met mechanics that have been around for 40+ years like your Father and they don't know half as much as the Mechanics that work for me that have been wrenching for maybe 10 years. Honestly, yes the Manufacturer's recomendations are a little too frequent, but by no means should you go 100,000 miles without ever changing your Differential Fluid, that's just stupid. On my HE gear usually we change the fluid once a year, sometimes twice depending on how much use the gear gets, I would recommend the same for your vehicle, about every 12-15,000 miles.
I'm not exactly sure what the torque specs are for the 8.25" rear end, but the 9.25" is 25 ft-lbs for the bolts, which you should be able to do by hand with out the need for a torque wrench. I just used a wrench instead of a breaker bar to get underneath the sway bar, and was able to pull the cover off that way. I would remove the spare tire before starting because it opens an amazing amount of room to work under there especially if you have access to a lift.