Thank goodness for how-to videos! I was able to get the part diagrams and instructions from AppliancePartsPros. I watched several other available videos out there to make sure that the information is consistent. As a middle-aged woman who works in an office, I was able to identify the most likely cause - the igniter, because I couldn't see a glow from the bottom viewing hole. At least I had a pretty good idea that this was the first thing to try from reading other reviews and several videos. While I was prepared to test the bad one before installing the new one, there was no need. It was easy to see the part was missing a chunk..
I ordered a new Rear Drum Bearing Sleeve as long as the drum had to come out since my dryer had been noisy for a while too. We'd already changed out the bearing slides, the Dryer Drum Front Support Bearing, and the trap duct asm the previous year, and those parts still seemed ok. The rear drum bearing sleeve was easy to install with the drum out, and that part did the trick.
Installing the igniter isn't an easy fix because of where it is. My boyfriend was able to change the part but it has to be done by feel. Putting the drum back in was tricky too because you can't SEE the pulleys, you have to feel your way with those parts too. He has experience working on cars, I don't think I would have been able to do it myself. Together, we make a good repair team, because finding the right part to change is just as difficult as changing it.
Seeing that appliances have a long lead time right now, I was up and running faster than if I had gone out and ordered a new one. Repairing your own appliances is very rewarding!