Thanks for the question.
Can you feel frost on the freezer panel and is the freezer fan going, also can you feel warm air coming from the front bottom grill
The defrost cycle isn't working, look at the part # XXXXX its the defrost thermostat, this part will cause the frost to build up and the heater as well check both parts its a meter if you have one.
The freezer coils were behing a panel in the front part of the freezer and they are frosted u
Sorry I lost the last response. How much would it cost to replace this unit? Would you suggest buying a new refrigerator/freezer?
You can repair the fridge by replacing this part, its a cheap fix for you and you can replace this yourself, just unplug the fridge when you replace the defrost thermostat.