Why did my refrigerator stop cooling and freezing?

six your old Maytag - still plugged in and running - all the food in the freezer has defrosted - dont know how long it takes to defrost a turkey - but it's ready to be cooked right now and it is still in the freezer! Both the freezer and the refrigerator are on the highest setting - that hasnt changed since I bought it. Could it be the motor or compressor? And how expensive is that too fix