How do you replace the alternator on a 1999 Chevy Silverado 1500?

Disconnect the negative battery cable. Loosen the anchor bolts on the alternator. Use a belt tension release tool (or a ratchet will work) to release the serpentine belt. Turn clockwise to release tension. Pull the belt off of the alternator. Disconnect the plug wire from the alternator. The release tab is on the back. Disconnect the ground. Remove the anchor bolts and pry the alternator out with a screw driver. Install the new alternator and go in reverse order. Connect the negative battery cable last. FYI it may help to use a standard screw driver to remove the air filter from the front of the motor and push aside. This will make it easier to access the belt tension pulley underneath.