Well, for the flip side of Buliwyf, I have EVERY confidence in the exact same front axle that's in your 8.1L 2500 'Burb. In factory form they hold up to 1000+ ftlbs of torque drag racing in 4wd... Add someone's shoddy lift kit, or a 22 year old kit driving a truck that isn't his, all bets are off, but for those of us driving it like we paid for it, you'll never break it.
One tip that's worth mentioning... Don't wait till you're stuck to put it in 4wd... put it in 4wd before you need to, and give the front CAD a little time to engage before you send a bunch of torque through it. If you do have to shift in and get the front pulling from a stop, go gently forward then reverse before you get on the throttle. That'll make sure the CAD splines are fully engaged and don't fail because of a lack of engagement.
You'll notice that everyone's advice is a little different, from "just go" to "OMG you're gonna die!!". That's because "Forest Service Road" means different things in different parts of the country. Many of them are nicely graded gravel roads, but some become exceptionally slick with rain, and others can be rougher than heck, or washed out in places, and fairly tight. You know the type of roads you're going on, and it's going to have to be your call what you do.
I'm running the truck version of your Burb, and I'll tell you I'm not excited about "wheeling" my truck with the truck camper on the back. It's just not fun. If you're towing a trailer, you're most likely just running the graded roads, with the occasional muddy or sandy spot or washout to get through. About the only modification that I'd consider a mandate for that is tires. Get some decent tires. I went from Michelin all season's to the new DC Fun Country tires and it made a HUGE difference in my ability and confidence when the going gets less than firm...
I wouldn't sweat it if you don't have the locker... I have it and it's never engaged while I was heading somewhere with the camper in the back. You're in an 8000lb truck. If the road is so washed out that you can't keep all four tires firmly on the ground, you don't need to be pulling a trailer through whatever it is you're considering... And as long as the wheels are fairly firmly planted, a locker doesn't do squat.
Make sure you have decent tires, and then head out. You'll learn pretty quickly what else might need improvement, but my guess is that you're looking pretty good for what you're going to be doing.
And post some pictures of the rig out and about!!
Chris