Aloha Disfanshan,
As Amw1064 said there is a lounge to shower and clean up, I believe you may want to reserve a time slot to use it in advance. It is right next to the Pau Hana room or Community Hall as I recall. We didn't use it for any of our trips as we were headed to Maui from Aulani. You must be an east coaster for your flight to be a red-eye. For those of us in the eastern half of the U.S. mainland, flights leaving Hawaii for home are almost always evening flights.
Amw1064, I feel your pain. We are headed back to Maui next May and had to pay a good $200 -$300 per ticket more than we usually do. Lots of folks say the fares should drop as you get closer to your dates but I always find that a bit scary myself. But I think the main reason I don't like waiting is that we try to book coach and upgrade with miles and that's another whole ballgame! Have you signed up for
www.beatofhawaii.com? It's a great site, no fee at all, and will keep you posted on airfare specials and happenings in Hawaii. Keep watching those airfares and keep the cookies cleared on your computer for the airlines sites you are checking the most. I'll say a prayer you find better fares to go back to your new home resort!!