The campgrounds at White Rim need reservations to get in, I'm not sure how full the are at this time of year but I'd check before you go in.

This is from the Canyonlands National Park Website:
Reservation office staff are available by phone to answer questions and assist with trip planning Monday through Friday, 8 a.m. to 12:30 p.m. (MST), at (435) 259-4351. When our workload permits, phones may be answered until 4:00 p.m. Please have a map available if you would like assistance with trip-planning. Reservations may not be made over the phone.

If you do the trail anyway start early in the morning so you dont get stuck out there in the middle of the night.
And Ian's right its a very easy trail, if you enter through Potash I'd rate it 1/1.5.
If you go in from Cannyonlands and go down the Shafer Trail the I'd rate it a 2, just because the switchbacks are so foreboding.

Have fun, Moab Rocks!!