Suburban is a steel tank that is Glass-Lined hence the need for that anode rod (drain plug)
Personally I would NOT use an impact wrench because of the glass-lining.
Use a 'cheater bar' to break it loose (yes you will have to remove burner tube so you can get better access)
Kinda tough to get heat on tank and NOT drain plug due to lack of tank exposure
Anode rod/drain plug is 3/4" NPT so threads on plug and drain hole are tapered -----cranking down on it is NOT needed to make it seal
Once you get it out......get a 3/4" NPT 6" steel nipple and run it in/out to clean up threads (cheap thread tap)
Then install new one until hand tight then snug up with socket/ratchet ----teflon tape is good to use with the steel to steel threads