Our refrigerator has been working until Saturday when it stopped producing cold all together. The temperature in both the Freezer and Refrigerator has been going up and down daily, freezer going up 15 degrees, then dropping down to negatives, Refrigerator as high as 45-37. Lights, Fans etc seem to be working. Replaced Thermistors, 2 in Freezer 1 in Refrigerator. I was told it could be anything from Main Board to Compressor. Any ideas? should I just pay to have a service tech come out?