Razoo, from all the reading I have done you dont need much to stock up on.
Uni's
diff cups
I recommend a spare clutch, it sucks when your clutch dies and you don't have a spare. I tried a traxxas clutch and the clutch is to light an the spring to hard to work right.

Element, All you need to do to run in snow is waterproof the elctronics. Take some RTV or similar sealant and go around the joints on the reciever box, put a little around the cord going in to the servos and you are good to go. Just make sure you do a good break-in on it.