You have made a wise choice. XC skiing is the BEST off-season training for triathlon. The advantages are numerous.
1. Get some good equipment( see Dev's post) and take a few skating lessons.
2. The skate technique is better for the cycling specific muscles. The classic technique is better for all around fitness, more closely related to running and better at keeping Heart rate low and going for longer efforts until you get very efficient with the skating.
3. To get full advantage of it you will need to ski 2 - 4 times a week for 2 - 4 months. Skiing a handful of times will not do much.
4. Go on a ski holiday for a week ski every day and really immerse yourself in the nordic experience.
If you do it right you should be able to jump back on your bike in late March and be able to go out for decent bike training rides almost right away.
Steve Fleck @stevefleck | Blog