just took ours apart sprayed O ring lightly with silicone spray 1. used long thin straight screw driver and went through fill opening . 2 used screw driver to push O ring into the holder and kept working it around 3. used needle point pliers to grasp the valve stem and pull it out. note vanes on stem are brittle and break off easily best to use all new parts. stem, rubber O ring and spring.
after removing O ring believe following would be faster and much easier
1. use pencil with erasure to push valve stem into container and exposing rubber O ring inside container 2. while still pushing in on valve stem use an EXACTO knife with sharp blade and cut the rubber O ring in two then use screw driver to free cut O ring and allow it to fall into container. 3. using the needle nose pliers grasp valve stem and pull out from container. tip container over to remove cut O ring
be sure to have replacement valve stem, spring and new O ring to replace in container. use some plumbers silicone grease to coat new O ring. assemble O ring onto valve stem in groove put spring on valve stem and insert into container body hole, push valve assembly into container might use the erasure on pencil to do the pushing. watch end of valve stem so it goes into guide inside container