The Sama-Sama transit hotel is in the Satellite terminal, which is linked to the Main terminal via the airside aerotrain. When you step off the MH flight, head for the C gates and board the aerotrain. The hotel should be fairly easy to find after getting off the train.

Wake up the next morning, head to the transfer desk in the same Satellite terminal to get your WY boarding pass.

If you have checked baggage you'll have a few options:
1) Convince the MH check-in agent at your point of departure to tag it through. There's a 50/50 chance this will work, as not all agents (esp. outports) are familiar with this, and they're not obligated to do so. If it works, just follow the steps above, and show your baggage receipt at the transfer desk to make sure it's in their system.

2) Should option 1) fail, tag your bag to KUL, but don't claim it until the next morning. Go to lost and found at the crack of dawn, go through customs, then take it upstairs to departures to check in at the WY counters. However, this would defeat the purpose of avoiding immigration queues. That said, if you get there before the long-haul widebodies start arriving around 6:30-7am, it shouldn't be too bad.