Welcome to AmSnow!
First, let me ask if you’ve found the maps you want for snowmobiling? I’m stating the obvious, but your GPS does not come preloaded with snowmobile trail maps. Many state DNR websites offer downloadable trail maps. You can also checkout websites such as www.travelbygps.com or www.redpinemapping.com which offer features with their maps like turn-by-turn directions, POI destinations, etc. In any case, your GPS needs to be compatible with whatever your navigation preference is.
Second, I’m not sure what kind of GPS unit you have so I can’t really say if it’s suitable for use on a sled. My initial reaction is probably not. You’re going to want something that’s designed for outdoor use and can take a few bumps and bruises.
The constant bouncing and jarring around, snow, rain, ice, freezing temperatures, etc. is akin to electronics Hell. Cold temperatures and moisture are not kind to battery life and LCD displays. Whatever you have should be water resistant and have the necessary accessories to connect to your sled’s battery. You should also pick up a local paper trail map as well, just in case.
The sites I mentioned have maps compatible with Garmin and Lowrance which can be downloaded for around $40-$50. Magellan has its own North American snowmobile trail map available for download for $50.
You could also look into smartphone apps as well. Trail Systems (www.trailsystems.com) has some pretty cool products coming out. Ram Mounts also offers a variety mounting assemblies you might want to check out as well (www.rammount.com).
Happy trails, and welcome again!