Okay so this Sunday I am flying out to Poland for the holidays
and I am most certainly taking all my gear with me, I am however a bit worried as to how it will deal with the harsh European winter conditions, with it snowing and being pretty much at a constant negative temperature and at times dropping well below it.

The main two main things I want to know about is preventing condensation on the gear when going from a warm environment (heated home) to out side.
I've heard inserting the lens/body into a air tight plastic bag whilst inside and taking it out side, could somebody please elaborate on this and if condensation were to occur how bad is it for the gear, will it work fine after a few hours, does it increase chances of fungi developing etc.?

Secondly Shooting whilst it's snowing. I never use my camera in the rain, so what would the deal be with it snowing and using it, any advice would be greatly appreciated.

and just reminding none of the gear I have (listed n sig) is weather sealed :S