On Ebay you can restrict the search by country, but it's perfectly normal to trade internationattly espcially considering these are Russian watches. Shipping cost is specified in the auction, and you do not pay taxes or fees of any sort.
On YouTube, like most videos on the planet: https://www.youtube.com/channel/UC7vSOnpUocYq0z8oiYFk0zQ
The kits are OK for opening and closing (most) cases and little more and generally pretty poor quality, maybe they include with an assortment of spring bars. But anything is better than nothing to begin with.