Be aware the "season" is coming to and end and you might be outside for a long, long time. Are you aware of sites like spaceweather.com? You want to be looking at sunspot activity.
In terms of photo equipment, a 50mm that is quick is a must, as is something wide (I took both a fisheye and a sigma 10-20 when I went to Norway). A strong CARBON FIBRE tripod is a must, as are plenty of warm clothing, a red light, a cable release and mittens/glove inners. You need some good, warm socks as well - you feet WILL get cold, as well as plenty of good thermals (don't be frightened to spend the money!). Make sure your gear works in the cold. I found my sigma 17-70 didn't like it at the top of a mountain and couldn't really change it. Condensation is also something that you will need to watch out for...
I would strongly recommend going out and trying your gear at night in the cold if possible so you get a feel of what is might be like in Alaska. There are lots of tutorials out there. I found this one
Learn how to photograph the northern lights to be useful.