kga109, as far as the MT sticker you won't need it as long as you have a current UT sticker, spark arrestor, and are sound legal through tech inspection. Other than that bring a good attitude and you'll have a blast.
The soil up there is far better for knobbies than trials tires. Many sections of the course are more sandy and loose. Yes, there are plenty of rocks but nothing like the Big Sky XC rocks either.
There is plenty of area there on the west side of the hill. I'm not sure how the course will be laid out this year but the area of the Homestake exit there will be plenty available which is similar terrain/trails. The race is held on the Pipestone side of the hill which will have tighter trails and terrain for the race. But at least you'll get a feel for the dirt and surroundings some.
Basically look at the map and anything west of Delmoe Lake should be ok to ride. If this is incorrect Jamey or Joe will chime in.