When you do replace that mobo, you most likely will get a reminder about authentication of Windows - a motherboard is one of the major triggers for that - but you shouldn't have to reinstall Windows. For all of the badmouthing that people do about Microsoft, I've never had any trouble getting them to re-authenticate when changing out components that trigger it.
Before you start the swap - backup your stuff that you want to keep just in case. Then go for it. It isn't that hard and very educational.
Good luck.