I hunted this unit once, over 20 years ago, and was lucky enough to get invited along with some guys who had ranch access. I agree with Top Gun, this unit is more known for white tail and turkeys, but there are mulies there, and some darn nice white tails. It is a tough unit to hunt from an access prespective without pre-arranged ranch access. That being said I would strongly recommend a good GPS with a land owner chip, regardless of where you hunt in this unit. There is National Forest and some BLM land to hunt, as well as some State land along the Belle Fourche river. River bottoms usually mean white tails, but there are some really nice ones out there, so your choice.
We stayed in Alzada Montana on our trip out there, and there are several 'watering holes' in town where you may find help and advice. I recall several evenings when some of the local ranchers actually came to town looking for hunters so they could supplement their income with some pretty reasonable trespass fees. Again that was a while ago, so I can't speak to the current situation.