Using the rating system found here
http://www.rr4w.com/ratings.cfm I would rate it somewhere between a 4 and a 5. I think any stock XJ could get through it but you have to understand, this trail is very long, very bumpy and the added cushion of taller aired down tires and suspension travel would be a major advantage.
As far as requirements:
Enough gas to get your rig 200 miles. There are no fuel stops from the time we leave Moab until we return to town. While your jeep may go 300 miles on a tank on the highway, it won't for two days in low range.
Food. My plan is to leave early Tues and get back into town sometime on Wed. That's lunch, dinner, breakfast, lunch and possibly dinner.
Camping gear and firewood. There is nothing to burn on this trail. A good campfire is a requirement if you plan to camp with me.
Tools and such. This isn't a technical trail but like I said, it's long and bumpy. It can take a serious toll on an ill prepared vehicle. Make sure stuff is good and tight before you leave and bring tools to fix what you forgot before we left.