Installing a bathroom sink in a vanity is made easier by the fact that the supply lines and the drain all remain hidden within a cabinet. If the cabinet has no back, simply attach it to the wall so it encloses the plumbing. If the cabinet has a back, you'll need to measure and cut three holes for the two supply lines and the drain.
Choosing a cabinet and top
High-quality vanity cabinets are made of hardwood to resist water damage. Less-expensive cabinets are made of laminated particleboard that quickly disintegrates when it gets wet. A vanity top typically is a single piece comprising the bowl, countertop, and backsplash. Acrylic or plastic vanity tops are inexpensive, but they scratch and stain more easily than other materials.
Two to three hours to install a basic cabinet and vanity top with faucet
Drill, level, hammer, screwdriver, adjustable wrench, groove-joint pliers, basin wrench
Installing a faucet, attaching a P-trap, connecting supply tubes, simple carpentry
Shut off the water and remove the old sink
Vanity cabinet and top, faucet, P-trap, supply tubes that fit the stop valves, plumber's putty, wood shims, screws
To install a drop-in self-rimming sink, first install a laminate countertop or, for a tile countertop, plywood and concrete backerboard. Many sinks come with a template for cutting the countertop. Otherwise, turn the sink upside down on the counter and trace the outline of the rim. Draw a line 3/4 inch inside the first line. Cut this second line with a saber saw.
Plumb the sink (Step 3). Apply a bead of bathtub caulk or a rope of plumber's putty around the hole and set the sink. If the sink doesn't have mounting clips, apply a bead of silicone caulk instead of putty. Set the sink in, wipe away the excess caulk, and wait several hours before attaching the plumbing.