Turn the sink's water supply off, and turn off the power source to the garbage disposal. Disconnect the plumbing to the old faucet, and remove the faucet. Set the new faucet into place, mount it according to the manufacturer's instructions, and reconnect the water supply lines. Turn the faucet on to check for leaks.
If the drain line, P-trap or garbage disposal blocks access to the water supply lines, remove it. To disconnect the water supply lines, use adjustable pliers to loosen the compression nut that is located near the sink's shut-off valve.
Use a basin wrench to remove the nuts located at the base of the supply line located directly under the faucet, slide the nuts over the supply lines to remove them, and lift the old faucet out of the sink. If the supply lines are glued to the existing faucet, use pipe cutters to remove the supply lines, and replace the supply lines with braided stainless steel lines.
Scrape the old putty or other adhesive off the faucet installation site with a putty knife, and clean the installation area with a heavy-duty cleaner. Reconnect the supply lines after mounting the faucet, and replace the P-trap, drain line and garbage disposal. Turn the water supply on, and turn the faucet on to check for leaks.