Agreed: if he knows of MUD, then it won't be a surprise.
I might second the Toyota Trail Team events.
I might also suggest buying him some unobtanium for his 45. Unless it's a pristine recent restoration, then there are without a doubt little things that it needs.
A restored heater, Aisin hubs, etc....
If you could sneak a picture of the vehicle here, then some quick direction on parts would be possible.
I really don't think anyone needs a "course" in offroad driving (but I'm a mountain boy, maybe it comes naturally to some), so just tracking down the local cruiser club might be as or more effective (especially if his 45 runs).
Dan