The road isn't as bad as it is made out to be in my opinion, I've driven that road numerious times and have never had an issue. A lot of people have trouble because they don't drive to the conditions of the road, last March I drove that road (snow covered, 2 days after a big snowfall) I made the trip (I believe it comes to around 560km) in less then 7 hours.
As for the temps, the ones I posted earlier are more common in January, and less frequently in Febuary, rarely do we get it that cold in March, but I threw it out as it is a possibility. Normally by March the snow is very slowly starting to melt and -20c is probably on the colder end of things. But like I say it is a possibility to have colder. With a little bit of wind it is cold, and white out conditions are regular.
As for the race itself I haven't entered, though I have a buddy that has, he ran it on a 03 Venture RS (not 100% sure on year but I believe it is 03), him and his partner didn't finish as they ran into some mechanical trouble on the return half of the trip. One thing you really want to be prepared for is hard conditions, I'm not sure if they did it this year or not but last years race they plotted the course during the summer months from a helicopter, making for some interesting areas to get into.