I have a fairly old Moen tub/shower faucet. The diverter is a 1/4″ pin in the faucet escutcheon, an arrangement I don’t see in the plumbing parts sections of hardware stores. Now the diverter is very hard to push in. Do I need to replace it? Can I get parts? Or can I replace the whole setup without having to get behind the tiles in the wall? Before I call a plumber, I’d at least like to know what level of repair I’m likely to be in for.