JJ Surfer, thanks for the clarification.
Folks: I found what appears to be a good fridge tech. He'll be coming out this Monday morning to look at the unit. At this point, I wanted to have someone more knowledgeable come in and help me figure this out. I'm pretty sure that ice is probably blocking the airflow, but I want to find out what causes this so it can be fixed. Yes, I can unplug and defrost the ice over several days, but if the underlying condition is not fixed, it will happen again. I will report back next week once the tech has come and gone.
Thanks to everyone in this Forum!