Amy,
You should get used to the mask pretty quickly. I was sleeping through treatment about half way through. Make sure that they put the pillow under your legs and ask for a blanket if you are cold. They keep the treatment rooms well air conditioned as a rule. The mask will feel looser as you lose weight as well. They are typically a little tight in the beginning, probably taking that in mind. Also if the neck positioning device is backwards or for a different patient let them know immediately - that can make it very uncomfortable.

Another tip - make sure that YOUR name is on the treatment plan on the computer monitor.

I'm amazed that they don't have a stereo or boom box in the room. You can bring your own. Make a CD of your favorite tunes. That's what I did.