How big is your toy hauler?
There are 3 canyons to go up to get up on top of the Book Cliffs and all of them can be a bear to get a large trailer up. The best way is to come in from the north on the Oray Rd. It is oiled just about all the way to the top of them. You have Hay Canyon, East Canyon, and Bittercreek Canyon. East Canyon and Hay Canyon are accessed off of I-70 and the Westwater exit. Bittercreek Canyon is about 2 miles inside of the Colorado border off of old HWY 6. I have seen people take a 5th wheel down East Canyon but not up it. There is one switchback that you need to navigate. Hay Canyon is steep and Bittercreek can be just a plain mess.
The main roads are fairly good gravel, however if wet they might be a problem with a trailer
The rzr will be a big help to you. There are roads all over up there. I believe that the only source for maps is the BLM Land Management Maps that you can purchase for $4 each at a BLM office.
The nearest gas will either be Thompson Springs 5 miles east of the Moab turn off on US 191 south or Fruita, Co. 18 miles inside of the Colorado border. Fruitia may be the closest since if you come down to the south you will come out at the Westwater exit on I-70. If you go north to Vernal it is 50+ miles to town, but then it is 50+ miles if you go south.
So while you are there be prepared for the worst. Some people have a lot of problems with tires up there, the gravel likes to eat anything other than 8ply tires.
As for where to look over the deer. Tom Patterson Ridge, The Divide Road which runs all the way along the top from Colorado to the west border, Mc Cook Ridge, and the little pockets to the south off of the Divide Road from Mc, Cook Ridge to the east.