Remove the shower drain cover’s screws, and put them outside the shower so they do not fall down the drain opening. Grab the grates in the drain’s cover with needle-nose pliers and lift up to remove the cover from the drain opening, setting it aside as well.
Insert a slip-joint pliers’ handles into the drain opening, and slide a screwdriver between the pliers’ handles. Expand the pliers' handles so they press against the inside of the drain body as you turn the pliers and the drain body counterclockwise using the screwdriver.
Insert a long screwdriver into the drain opening in the shower pan, and push the drainpipe to the side 1/4 inch. Grab the rubber gasket, metal washer and nut that sit between the top of the drainpipe and the underside of the shower pan, and pull them out through the drain opening in the shower pan.
Slide the new drain body’s rubber gasket and washer into place on the top of the drainpipe before releasing the drainpipe slowly with the screwdriver. Spread silicone caulk on the underside of the new drain body’s upper lip before threading the drain body into the drainpipe by turning it clockwise.
Tighten the drain body in the drainpipe using the pliers and screwdriver you used to remove the old drain body. Place the new drain body’s cover into its opening, and tighten the retaining screw.