Maytag Heavy Duty Dryer, electric.
Model DE313 Serial 256802VT
With Auto dry feature on permanent press & regular cycles.

My dryer normally will stop when clothes are dry, and sould a buzzer.
Last week the dryer did not stop when dry and continued to heat for a couple hours. Nothing caught fire.
Now the dryer won't heat at all.

I've done some trouble shooting today, here is what I've found.
1. The heater element is broken and will need to be replaced.
2. I tested the Hi Limit Tstat for continuity. This is located on the blower housing to the right of the fan. Between Purple & Blue/Gray the cont. was good. At room temp and after heating there was no cont. between Purple and Orange
3. There is what looks like a second Tstat mounted to the heating element housing.
I have not tested this.
4. The door switch is working, dryer turns off after opening door.

I'm asking the forum for support on a couple questions.
1. What was the likely cause of the Auto Dry function failing? Which likely burnt out the element.
2. Because of the age of the machine does it make sense to replace both Tstats at the same time as the heating element?
3. How to check continuity on both of the DE313 Tstats.
4. If there is a fuse, where is it located.