I was there last spring/summer and drove up the Alaska Hwy and down the Cassiar. Of course, with my rig I was able to take many interesting back roads, which you could not. But if you stay on the main highways you will have no trouble. I found the worst (highway) frost heaves on the Tok and the Taylor but you needn't take those. Some frost heaves are bad enough to pitch your rig off the road if you're not alert. Watch for squiggly center lines.
Most of the highway conditions were superior to those in the lower 48 but the Yukon stretch mentioned above was many miles of mud and gravel and not a lot of fun. It may be finished by next year.
I loved it up there and can't wait to go back! :)