Waterproofing your electronics is not too difficult. Buy a few balloons from the dollar store and put them over all servos, battery pack and radio receiver. If you use a failsafe put one over that too. After you put the balloons on use some sort of sealant, like rtv, around the opening of the balloon then either use a tiny zip tie or a twist tie, like on a loaf of bread, to secure the opening and you're done. Remember to remove your servo arms before applying the balloon and after you put the balloon reapply the servo arm. Only puncture once in the balloon with the screw to sevure the arm. You should replace the balloons at a minimum whenever you change arms or take off the arm for whatever reason.
As far as water entering the engine, even the most careful of us can have a little water enter the engine from time to time. I recommend using more air filter oil to keep the engine lubed a little better to prepare for a little water entering the engine.
If you so have a large amount of water enter the engine, I mean pretty much completely submerged, remember your engine will be running at over 200 degrees and you have the potential to crack the block, head, piston, crank, etc... when going from really hot to really cold. If there is no damage in the moving components then take off the air filter and remove the glow plug. Disconnect the fuel line and dispose of the possibly tainted fuel. Crank your engine with the carb fully opened and the engine vertical, like with your rc standing on it's tail. The best method is a little past vertical with the carb higher than the head. Add a little amount of fuel and repeat cranking several times. Lastly add a small amount of afterrun oil and repeat cranking again.
Reinstall your air filter, ensuring it is dry. Reconnect the fuel lines and try to start your engine. You engine will be pretty hard to start however if will start, 99% of the time. Your engine will not run very well until all of the residual after run oil and water are completely out of the engine. At the popint you get your engine started I would suggest, if you can and your electrical system still works, running at least a tank through it at about 1/4 throttle. Last step will bo to go back to running however remember to expecially add some afterrun oil after this session and make sure you work the oil in before storing your rc.
Bottom line here, don't be afraid to run in the snow or a damp environment just remember to be careful.
