GAAA!! Driving in the SNOW?! 8^O Well, I guess it's supposed to be do-able. The ESC is supposed to be water proof. But I wouldn't recommend it, mate. Besides the electronics, there are metal parts that will rust if not thoroughly cleaned and dried (suspension arm hinge pins, bearings) and frankly, I do not believe them when they say the ESC is waterproof. Be careful. Being a brushed motor, there's no issue there, except for the shaft ends that will need lube.
If you get to the point where you want to go brushless, I highly suggest this motor system: http://www.hobbypartz.com/ezrun-35a-9t-3650-motor.html
Perfectly suited to the Evader, fast and reliable. I have two of them and they're great. Can't beat the $77 price!! Just be sure to dump those crappy battery connectors and change to something like Traxxas connectors. Those Tamiya Molex connectors cannot handle much current and will melt, even with a 7-cell NiMh. (Oh, and don't use NiMhs if you go brushless, they can't handle it. Gotta use LiPo)
Let me know if you have any other questions. Happy to help.