My gas dryer ran fine, but there was no heat. I didn't hear gas igniting, and when I looked in the lower access panel as the dryer was running. I didn't see the igniter start to glow.
This website suggested that the problem was either the igniter or the thermostat. I confirmed that the igniter was dead by using a multimeter, following directions on a video I found on the web. I wasn't sure about the thermostat, so I bought it anyway.
Replacing the igniter was a simple 5-minute process using just a screwdriver.
Replacing the thermostat was a little more involved because I didn't have the right tool to reach one of the bolts. So I ended up having to take off the front of the tumbler which turned a 5-minute job into a 20-minute job.