Refrigerator Not Cooling due to ice buildup on coils

Removed shelves from freezer section and removed protective cover using a screwdriver and nutdriver. 5 screws.
Upon removal of the cover, I noticed the coils totally cover with ice. At this point I noticed that the defrost heater was burnt out. I removed the heater using screwdriver and pliers and tested the heater according to instructions from Parts Select website.
Since the coil was exposed, I also tested the defrost thermostat according to Parts select instructions and found it to be working properly. i also tested the defrost timer and found it OK.
I replaced the heater, closed the protective cover, replaced the shelves and plugged the unit on.
It has been working just fine since then..
In addition to saving money, i saved myself the agravation of looking for a repairman and having to wait for THEIR convenience to to the work.