Check out other road trip threads on Alaska, Alaska Hwy., etc. I, too, wish we were going this year. Most of the Alaska Hwy is a wide, well paved and maintained highway. When you get far enough north, the road starts deteriorating with frost heaves (well marked with red flags by the highway plus signs), but is generally a good road. There's always construction somewhere. I can't remember any particularly scary heights, though some other roads can have those problems. The roads in Canada are generally better than the ones in Alaska.
We love to visit northern Canada. Good paved road all the way to Dawson City. There's a very good Italian restaurant in downtown Whitehorse that I can't remember the name of. You can drive to Inuvik on the Dempster—400+ miles of well maintained gravel, but if it's wet, stay put with a trailer—very, very slippery. You also need very good tires for the Dempster or most other dirt and gravel roads up north—many have shale mixed in and that stuff eats tires. The ferries over the rivers on the Dempster can be a problem if you have a long overhang. You can also drive to Yellowknife, NWT, on a paved, though sometimes bumpy road. Great things to see there too.
If the Milepost doesn't arrive before you leave, surely they're in large bookstores in Calgary and Edmonton. I've seen them in Colorado bookstores, though I have always ordered them by mail. You have to have it. CAA/AAA tour books is weak, map is too small. Get one or two other travel books—lots to learn, to know. The trip is better if you read up on everything you can.
Mosquitos are being born now and waiting for you. The little ones seemed to be the worst ones. Some days are awful, others not bad.
We've been to Yukon twice, NWT once, Alaska twice. Maybe again next year if we can deal with the gas prices.
Let us know how it's going and send pictures.