Hi, The small push/pull lever? for sending water to shower head, is that called a diverter valve? Anyways ours leaks into the tub and is stuck/seized for years now since we only use the shower now. I assume I will have to shut off water?, remove the main faucet valve knob & cover/plate screws for starters...is this a straight forward/easy job and are the parts/seal available anywhere being it's a Delta..but 24 yrs.old. What's used normally to seal around the downspout, just white silicone caulk?