I bought a new ignitor from APP and pulled the oven out to where I could get to it. The back access panel came off with a few phillips head screws, where I unsnapped the wiring connector.
Back around at the front, the oven floor came off without tools. One sheet metal screw held the flame spreader in. From there, the ignitor was visible, and required a 5/16 nut driver to remove the ignitor from the gas tube. Reassembly was in reverse order. The old ignitor had obvious signs of damage, and the oven works flawlessly now. Dead simple.