After you get your gear together in a pile, put half of it back in the house. Look at the money you planned to take, double it.
I've been up there twice. Except for fuel prices, you can spend as much or as little as you like. First trip was 5 weeks, and I camped every night. I bought food at grocery stores and ate from the saddlebags. I had no breakdowns, so no expenditures at all.
Look here:
http://www.themilepost.com/ There is an online version of last year's version somewhere.
Best trips I ever took. If you go in the summer (recommended for a bike!) take something for the bugs. The whole state is a swamp all summer long.