YMM is your typical industrial town, there is literally nothing downtown (about 15km from the airport) other than Peter Pond mall and a few restaurants/hotels and the casino. At that time of the night, about the only thing open would be a few bars and the casino. Most of the newer hotels are built in the industrial area right by the airport. If you are hoping to see the mine sites, the closest ones are another 40-60km on the other side of town and you wont be able to see it at that time of the night.

I know there is no baggage storage at the old airport but I am not certain about the new airport (opened this year). Even with the new terminal, it is still a small airport, don't expect much in term of services. If you want a rental car, must book ahead, almost no chance of getting one during the work week if not booked. Taxis are scarce, expect to call at the airport and wait. To me, a rental car is a better bet if you want to see the place as there is no definitive downtown, best thing is drive from airport (one end) along highway to mine sites (the other side of the city) and see how you have the new mixed in with the old and new buildings going up whereever there is room.