Jerry...If you are planning an Alaska trip this next summer you're in for heck of a fine trip. I have driven to Alaska twice with the last one in 2006. Don't know if you want any tag alongs or not but know of some Beavers wanting to also go on that trip. So to give you an answer to your questions as I see it, I hope it will help you in your travels. There are a lot of boondocking places on the way.
1. I would arrive at the Canadian border around the middle to last week in May as winter is in its last hurrahs there. The middle of September would be OK to return to the U.S. of A.
2. Maintenance: I would cover the headlights/driving lights with a 10 mil, or greater, plastic due to thrown gravel on the roadway. Use double sided tape to secure the plastic.
Place a full cover on the toad to keep it free of gravel on the windshield, water well, and headlights.
Carry an extra belt for the engine.
Other than general maintenance to the coach you should be OK.
3 As Gerald indicated get a copy of the Mile Post book as it is, to me, the Alaskan bible and learn to use it. It can be complicated at first.
4. Make use of all the visitor places as they are small museums along the way. Dawson Creek is a great example of this.
5. Drive on the top half of your fuel tank, but there are plentiful fuel stations.
Take your time, drive slow when you see marker flags on the side of the road indicating frost heaves or broken spots in the highway.
6. Take time to smell the roses and above all stay safe. Slow down and edge over to the side for on coming vehicles spraying gravel at you.