This won't answer your questions on source for needed parts, but I'll throw it out there anyway. For $2,000, you are a good bit into just buying a second bike so you have a dedicated snowbike and dedicated trail bike. I think many of us started out with the idea that we'd swap the bike back and forth between winter and summer. But we quickly realized that the bike and transmission that makes for a great snowbike are opposite traits of a bike that makes a great trail bike. Soon enough, most end up with two bikes and don't swap back and forth between wheels and track. Add a couple more thousand to that $2,000 part (plus install expense) and you can pick up a nice used bike for summer. That will save a lot of time on swaps twice a year (or more if your seasons overlap a lot) and, you can REALLY set up your snowbike perfect since a lot of the snowbike mods are not conducive to easy seasonal swap; mods such as a heavily modified/dedicated airbox and intake, tunnel cooler and radiator mods/delete and associated cooling hose reroutes and mods, resprung/revalved front fork, etc.)
I'd rather have two older used bikes setup up perfect for each duty (wheeled and snow) than one fancy new bike trying to pull double-duty. Having one bike for two seasons is all about compromises. True that using one bike for both is better than not doing both sports at all, but if you want the best trail bike and the best snowbike, there is no one bike that can be both. Consider owning two bikes to dedicate to each sport rather than sinking some big money into a single bike, like you are about to do, to try to make one bike do both.
