Sugarloaf is going to blow your mind! Definately hook up with Erik Beckman. Since you're staying on mountain, you'll get an "Activity Card" that entitles you to a free "Perfect Turns" group lesson each day - which usally ends up as a one-on-one with Erik :)
If you're staying in the Sugarloaf Mountain Hotel, there's a full size tuning bench in the ski locker area complete with power for irons and such. I've only stayed at the hotel, so I don't know the layout at the Sugarloaf Inn.
If you're at the hotel (and not the Sugarloaf Inn), then the ski lockers are on the ground floor to the extreme right while facing the front door. There are lockers both outside (called the Fridge) and inside where the tuning bench is located.
As Geoff noted, there are lockers in the main lodge, but you can just stash your stuff in a cubby, on top of the lockers, on under a table...
Oh, and make sure you hit "The Bag" for a Bag Burger and a brew!