Well I'm not seeing any diagrams online to locate what's what on your fridge so you'll have to locate certain parts on your own to troubleshoot this problem... By now you've already removed the frost from the evaporator coil to get this thing back to refrigerating but it'll just ice up again... My first move with an ice up is to locate the defrost timer and manually place it in a defrost mode by turning the small dial gently by hand clockwise until you hear an audible click... Wait at least 35 minutes to see if the timer returns the system back to the refrigeration mode, if it doesn't, then most likely the timer is bad... While it's in the defrost mode (with the inside back cover of freezer removed) observe what's happening with the defrost heater(s)... Any visual signs of defrosting happening??? It's possible the heater or the defrost end control (or both) are bad but you'll need a voltmeter to determine this... Some defrost heaters are tubular glass with the heaters inside and one can easily determine these are defective because you can see where the heaters have burned... Defrost issues are usually inexpensive to repair so it's worth it to determine what's wrong and fix this unit rather than replace it... Good luck!