I go every Oct, though I wheel my Jeep, not my truck. /ubbthreads/images/graemlins/smile.gif
Moab is a great place, the scenery is like nothing else you'll see. The combination of good wheeling and great scenery makes it a real winner. Your long wheelbase will be a big help on the ledges....that you can do with the long overhang, be careful that you don't waste your bumper. I've found tire pressure is critical if you're giving it a good try on the real steep climbs, but you probably won't be able to get that big truck up to them. The temperature also makes a difference, you can climb stuff at one temp that you can't at another, which I haven't experienced anywhere but Moab.
If you can get your long truck up Moab Rim, that is one kick ass trail both for the challenge and the scenery. Cliffhanger is also a great one, and ends at a lunch spot on the cliff overlooking the Colorado River. But, I understand that the mine is using the trail for a construction project and the trail is temporarilly closed. A good run for a partial day is to Dead Horse Point in Canyonlands north of town, then taking Shaffer Trail (which is a dirt road) which switchbacks down the cliff and ends down in the canyon with good looks down to the river, then ends up downriver from Moab with an easy drive back to town. The switchbacks could be a little tight for your long truck, but you should be able to do it.
Ask if you can run Hells Revenge with your truck. I think you can, I know any stock shorter wheelbase rig can run it. It is the premier slickrock trail, and has some really steep climbs and downhills, but nothing (on the main trail, anyway) that is super challenging....other than the pucker factor. It also has a great place to stop for lunch where you can walk out to the edge of the Colorado River canyon.
Wish I was going......but I'll be there in Oct.