Expect severe winter conditions, especially the further north you get.  If you don't already have 2 full size spare tires already mounted on rims, be sure to get them.  Of course, you will likely already have winter survival gear (warm sleeping bags, winter boots, gas stove, food, etc) but get that stuff as well if you don't. 
  
I'd 2nd the stop at Liard.  Even if you have to detour back down south a bit, it is well worth the trip.  Last time I was through there about 10 years ago, it was a full moon with amazing northern lights and beautiful steam coming off the water.  Certainly one of the most memorial nights of my life.  I think we were the only people there that night too. 
  
Have a great trip!