i didn’t even know kit.com existed. Seems like it might be useful for things like this.
Also, i’m happy that its even possible at all now to build an esk8 for $400 even if the deck or other stuff is preowned. It used to be pretty much impossible unless you had access to machines or a real shop of some kind.
Use a silicone sealant to seal your board. It will be fine. And try to use heat shrink on your connections if possible, it will minimize water/shorting damage.