I've been down a few times, first trip I just hung out at a trail head and luckily a group came along and welcomed me to join them.
Second trip I ended up cruising the campgrounds until I found a group going out and invited myself along
I strongly suggest finding at least one other vehicle to make the trip with you, it really does suck having to be worried about breaking and no assurance of help.
Oh yeah, it's 1816 Km from Cranston, I always made an overnight stop around Pocotello cause I'm too old to drive the 20 hours at once.
Oh yeah, you HAVE to stop at the big Army surplus in Idaho Falls, it'll take up a couple of hours of your time but it's worth it.
I'm planning a trip next Labour Day, it's the local clubs annual wheeling weekend and usually gathers a good selection of rigs.
If you go down on a regular weekend, you'd be surprised at how few rigs you see on the trails.
Here is a link to the local clubs site
http://www.rr4w.com/Good luck.
Vince