Turn the power off to the oven. Pull out the oven base and unscrew the nut holding the gas burner cover in place. Pull out the cover and place it to one side.
Pull the ignitor's plastic plug from its socket. If the ignitor's two wires are attached by ceramic nuts, unscrew them by hand. Remove the two screws holding the ignitor's metal cover in place. Remove the ignitor.
Attach the new ignitor into place by screwing in the two nuts into the holes through the metal ignitor cover. Push the ignitor wire's plastic plug into the socket. If the ignitor was attached with two ceramic nuts, reattach the wires to the oven wires with the ceramic nuts--by hand.
Turn the power back on and turn on the oven; if the ignitor flame is healthy and takes only a few seconds to ignite, it is working fine. Replace both the gas burner cover and oven base.