I've driven the Alaska Highway on at least 6 round trips. Take your time, and the road won't be a big issue, except for the washboard that you are BOUND to run into at several points.
In BC, make absolutely certain to visit Lliard Hot Springs. If you can get there when it is NOT tourist season, all the better. I understand that since I left AK, there are a lot fewer vehicles on the road, but I wouldn't let that stop you.
When you are in the Yukon Territory, make certain you have waders, bear spray, and a fly rod. At ANY given spot, if you walk a mile up the stream, you will catch more Grayling than you will know what to do with...only vying with the bears for those fish. Anything under a mile has been fished out long before you got there.
Lake Kluane is one of my favorite all time beautiful spots. Also...Lake Muncho is a definite must-stop.
In 1979, we drove down the highway from Fbnks to Minneapolis, and there was a 1 week stretch where we drove no more than 50 miles per day...had to stop at numerous camping sites...just to see them!
The suggestion for buying the Milepost is a must...no matter how you are travelling the road. The trip itself can be done in 3-4 days...but the best time I ever had was when I took 3 weeks to make the trip!
BTW, make sure you visit Chena Hot Springs when you hit Fairbanks. Fairbanks is also, by the way, one of the best bicycle touring cities on the North American Continent.
If you are interested in staying in a B&B in Fairbanks, let me know. I have a friend who runs the prettiest one you've ever seen up on Farmer's Loop Road.
Finally...if driving an RV, it is advisable to take the AK Ferry at least one way. That is a trip not to be missed.
-Kurt-