Remove old shower stall and install new shower stall. Cut water to house off or if there are cut off behind the tub cut it off there. Carefully remove the old tub and shower valve. Remove handle, and esuction plate. Cut old valve out from the back side wall Clean work area and begin prepping the new tub and shower valve for installation. Begin install putting the new tub and shower in place and solder together , then come back to the tub side of the faucet in install the tub a shower trim.