Lettuce turning to ice means too much cold is reaching the fresh food side, or the appliance is misreading its own temperature.
Common refrigerator problems
All refrigerator guides
Refrigerator Freezing Food It Should Only Be Chilling
Ice Maker Stopped Producing: Water, Temperature or a Jam
An ice maker needs three things to work. Establishing which one is missing takes a few minutes and avoids replacing a module that was never faulty.
Water Under the Crisper Drawers and Other Fridge Leaks
Refrigerators produce water on purpose. A leak means that water found a different route, and where it appears identifies which route it took.
Refrigerator Warm but Running: Start With the Freezer
Whether the freezer is still cold splits this diagnosis in half. Cold freezer with a warm fridge means airflow; both warm means something else entirely.