Superb navigation expertise is critical for the Alaska Mountain Wilderness Classic. Some people take along a GPS but if you do, you shouldn't rely on it too heavily. If you're stopping all the time to see how many feet you traveled in the last twelve minutes then you probably need to put it in your pack for a while and stop looking at it. A GPS can actually slow you down if you get mired in the minutia of the coordinates and routes.
Whether or not you take a GPS you definitely need a compass and a map. Most racers spend the months before the race poring over maps and figuring out which route is the fastest. By the time you start the race you should have studied the terrain and the vegetation of your route and considered what it will look like when you're there in person. Everything in Alaska is big so imagine the landmarks looking much larger in person than they seem to be on a map.
I have used a combination wrist altimeter and compass for past races and it's worked very well for me. Suunto makes great altimeters and it's the brand that most serious mountain climbers use. Read some reviews and buy what you think will work best for you. Here's the one I use. Suunto