As long as you have a reservation for DME you should be good to go. I always bring my paperwork with me in any case. I just fold it up and stick it in my bag. Your MB should work fine...they will have you tap it at the bus line, and it will show which resort, you are then directed to the appropriate bus line.
If you didn't make a reservation for DME, you should call them immediately. You shouldn't be allowed to ride the bus if you don't have an existing reservation.
Some people think it's automatic...as soon as you have a resort reservation, you're good to go with DME...but that's not how it works!!!