Unplug the power cord from the wall outlet.
Slide the oven away from the wall so you can access the back.
Pull the string away from the knob connected to the ignition switch to remove it.
Remove the two mounting screws next to the control knob shaft.
Remove the screws holding the upper rear panel in place. Lift the panel off the oven cabinet.
Pull the old ignition switch out of its compartment in the back of the oven. Install the new switch in its place.
Unplug the wires from the old switch. Plug them into their sockets on the new switch.
Replace the mounting screws on the front control panel next to the control knob shaft.
Replace the upper rear access panel. Install the screws holding it in place.
Place the control knob onto the shaft. Press down until the knob locks into place.