I was in a similar quandry prior to going to Kenya/Tanzania late last year with my PDX10. My key recommendations:
1. Neutral density filters - there will be LOTS of light, especially from the snow!
2. Polarising filter - to get gorgeous blue skies
3. Something to protect the camera from the elements (and provide a shade so you can see the LCD)
4. Definitely use the XLR microphone adapter to cut down on handling noise
5. A tripod to double as a monopod for action panning shots or a Chest Pod
6. Lots of batteries and a double high speed charging in case you are remote from mains power (or a car lighter adapter)
7. Lots of tapes - I took 20 for a 2 week safari and ended up using 17 (in DVCAM mode - 40 mins each)
8. If you can, a laptop so you have something to view each days' material on and, if you take a memory stick, something to download stills to
Setting white balance on the snow would seem reasonable especially if you really want it to look as white as snow(!)
I'd spend the first few hours with some of the skiers/boarders to get used to videoing them and trying different settings - hence, the benefit of taking a laptop (unless you can get access to a TV/monitor). If you are going to document "off-piste" as it were (i.e., dialogue), some headphones would be wise, too.
See
http://en.wikipedia.org/wiki/Lithium...ure_and_charge for info about battery life vs temperature.