Glad I came across this website. Affordable prices and very useful opinions from other users made it an easy fix. Refrigerator was freezing food, and I guess the little door that opened and closed was broken. There were 3 screws: one behind the air filter, the other on the left side where the hole is, and the last one was right under the water filter. The plastic covers come off easily and the whole diffuser unit can be easily replaced.
Thanks AppliancePartPros.