With occasional internal repairs, a modern faucet unit will last for many years. Sometimes, though it may start to stink and reach a point of no repair, or the exterior coating becomes worn or corroded. Replacement is not difficult.
Turn off the stop valves for both hot and cold water supply lines leading to the fittings. If there are no stop valves, turn off the closet valves in the lines between the faucet and the water heater and cold water supply. If necessary, turn off the main valve, shutting off the all water in the house. Open the faucet to drain out as much water as you can.
A rainbow wrench will save you a lot of trouble, especially behind a deep kitchen sink where pliers or other wrenches will not go. Use it first to remove the nuts holding the supply lines to the faucet, then to remove the hexagonal nuts that hold the faucet to the sink. The old faucet is then simply lifted out.
Take the old faucet with you when you are shopping for a new one. This will insure that you get the correct replacement size. If this is impractical, carefully measure center-to-center distances between pipes and note pipe diameters.
Check the new faucet for fit in the actual installation, nuts and washers will be benefit the sink. Wipe the top of the sink clean where the faucet will be installed. Most exposed-deck faucets (the deck is the part that conceals the various inner components) have a rubber gasket on the bottom. If your new one does not, put a ring of plumber's putty on the sink around the perimeter where it will be placed. Set the faucet in place, slip the washers over the faucet shanks from benefit the sink and turn the nuts onto the shanks, starting them with your fingers and tightening with the basin wrench. Then reconnect the supply lines, adjusting them as necessary to fit the new faucet. Turn on the water and check all connections for leakage.
If your sink stinks after you have replaced the faucet, you may have more work to do. The foul smells coming from sink drains are caused by soaps, shampoos and food going down the drain and clinging to the side of the drain pipe between the drain hole and the trap. Occasionally, this residue builds up, leaving a small hole for water to drain away. This will be noticeable as the sink will take longer to drain.
These odors can not be masked by using deodorizers or hot water.
To correct the problem, remove the center drop drain tail piece from the trap adapter. In kitchen sinks, it is typically brass or ABS plastic and in the bathroom probably chrome. Using sudsy ammonia and a bottlewashing brush, scrub the residual from the inside and outside of the tail piece. Replace in the drain and you will notice that the water will drain more freely and the odor will be gone.