Are you a military veteran? If so, I highly recommend contacting S.M.A.R.T. http://www.smartrving.org/
Their Alaska RV caravan begins at Dicks RV park in Great Falls, MT., and ends after crossing into the U.S.A. at Sumas WA. This is the least costly Alaska Caravan available, to my knowledge.
If you are not a military veteran, you may be "sponsored" by someone else in the caravan.
We went in "12"; it was the best time we've had in the last 20 years. Personally, I think I saw more in Canada than I did in Alaska, except for flying over and around Mt. McKinley/Denali.
When in Dawson City, YT; take time to "kiss the toe" for an unforgettable experience.