Yes, you should be able to rebuild the valve. Kohler seems to have a build of the day, though, and you need to get the right parts to do it; unlike Delta and some of the others that have used the same guts for numerous years. From what I understand, you'll probably have to go to a plumbing supply house and order the parts. Best thing is to probably take them with you. This can be a pain, as often you have to shut the house water off because there are no individual shutoffs in the shower. I've been told that the parts catalog for Kohler is more like a telephone book.