Replaced the main Cold Control in the refrigerator and the Defrost Thermostat in the freezer compartment. While I had the power off, I went ahead and replaced the compressor run capacitor, even though the old one still measured well within proper tolerance.
The three parts were so reasonably priced, I figured I'd replace the three most likely culprits. After watching the very well-done videos on the website, I tackled the job and had all the parts replaced and the appliance back up and running in less than an hour. Everything seems to be running just fine now, with the temperatures in both the fridge and freezer exactly where they are supposed to be.
I'll definitely be coming back to AppliancePartsPros.com for all my future needs.