Snow will really fool your camera meter - all that reflected glare off the snow fools the meter into thinking the light is much brighter than it actually is, which results in under-exposure. The answer is you need to give more exposure probably 1.5 to 2 stops more, but in the time honoured tradition I'd take some test shots and bracket like Hell to see what works best on the day.
I've never used a polariser on snow Sammy so I dunno what to advise for the best. The attraction of snow scenes and a deep blue polarised sky is obvious enough, but I don't think it will be that simple. The polariser only has a polarising effect on reflected glare from certain parts of the image, it will have little or no effect on the snow itself, but it will darken a blue sky or reduce reflected glare off, for example, water in your shots. The problem is that because the polariser has a filter factor (the amount by which exposure must be increased) it still has an effect on your whole image including the non polarised parts, and that is the effect of being a neutral density or grad filter, so while it may well produce the nice blue sky it will probably also give you dark looking snow.
My gut feeling is don't use the polariser, just concentrate on getting the exposure right. Certainly experiment with the polariser, but make sure you have some shots safely in the bag first.
Definitely shoot RAW to avoid white balance problems.
