Welcome to the club.
The first thing I tell new owners, if you are a first time buyer, the cheapest part is buying the HUMVEE.
Every week you will want to do new and more with it.
I just put a 6.5 in one of mine and the other is going to get a 6.5 with the 4 speed at some point here. Have the driveline just need to get the time.
Have fun and ask any questions. Most likely someone here has done to thought about doing whatever you some up with..
FYI Step one, change the fluids !!!