Alaska trip by L'Rover
I've done the trip from Edmonton to Yellowknife to the start of the Alaska Highway through to Skagway and back south to Cold Lake then west to Vancouver all in a late 70's 1000cc Austin Mini with 2 spares, and air pump and tire tubes/repair kit while carrying a lot of weight - including 43USG of fuel in cans.
No real issues, some problems none requiring more than 2 days in the same spot (blew a CV while in the blasting area of the Giant Mine while offroading...they weren't happy and towed me out to the highway where I fixed it on the side of the road - well enough to get into town anyway (used some rocks - the longest part of the repair, finding ones that would fit and be close to sperical) where I could visit the local scrapyard.
If you stick to the Alaska Highway and it's feeder roads from Canada or the US - they are all paved so no worries. As long as you have a mechanically sound vehicle, know when it sounds 'wrong' and what MUST be fixed -vs- what can be macgyver'd together (like an Austin Mini rear suspension lift using coins and an aluminum can).
If you take the FAR more interesting gravel sideroads (like the run from Ft. St. John to Wrigley) you might want basic tools and camping gear - I pulled the trans/engine using a tripod made of felled trees and a come-long (hand powered 2 ton cable winch) so I could fix an oil pan with a hole in it (my fault - Mini's ground clearance isn't the greatest and I was where I probably shouldn't have been...but in my defense they can go a lot of places you'd never think they could if you can pick routes well / drive aggressively) which took 3 or 4 days and a lot of blood donated to local mosquitoes. Traffic can be almost nonexistant at some times of the year although with oil and gas exploration usually at least 2 or 3 vehicles will pass per day.
I wish I'd have thought of the "wrong way round" concept (some pics were up on here a while back - it is being done in a Mini Estate wagon) when I had the time to do it. Now I'm anchored with work/wife and can't hare off accorss continents on a whim....
http://i231.photobucket.com/albums/ee132/fisher205/Alaska 2009/Alaska2009-07-25095.jpg
Get the Milepost magazine as a starting point...GPS might be nice but a decent set of low level 1:500k or so aviation maps will have topo and roads etc