Several months ago, the freezer was so frosted, it blocked the air cavity that brought cold air to the refrigerator compartment. The result was the freezer was cold enough, but the refrigerator was near room temperature. At that time I defrosted it manually with the idea that that would correct the problem. It frosted up again.
I defrosted it manually, then checked the schematic. There are three parts making up the defrost system: Timer, thermostat, and heater. I checked the heater with an ohm meter and got around 38 ohms. I concluded the heater was good.
Then I bought the thermostat and timer from Appliance Parts Pros. The prices were good, and each part included a video showing how to replace the part. This was extremely helpful and easy to understand.
I decided the problem was most-likely the timer and it was the easier thing to change since no wire splicing was involved.
From the video, I knew exactly what to expect and what tools I needed. The change-out had no surprises other than that I learned there is access to turn the timer with a screw driver to cycle through all its steps. Doing this verified the timer was working and the defroster was now working. I did not replace the thermostat, since I could tell from the behavior of the heater that the thermostat was doing it job.
The timer was an exact fit/drop in replacement. The whole replace operation took around 10 minutes, and that was because I was taking my time.