You can replace the kitchen faucet by yourself. If you decide to do it start by turning off both the hot and cold water using the valves under the sink. You'll need a basin wrench to get at and remove the pieces up under the sink. First you will loosen and remove the water lines and then the retainer nuts that hold the faucet in the sink. Pull the old faucet out. Put some plumbers putty on the sink and press the nylon gasket firmly in place. Thread the spray hose through the hole for the sprayer and back up through the gasket. Wrap some nylon tape around the nipple and then attach the sprayer hose to the new fixture. Drop the faucet into the holes in the nylon gasket and reattach the retaining nuts to hold the faucet in place and then reattach the water lines.