Looks like the problem is a bad ice maker thermostat. I would not waste time and money to fix the old ice maker because it can be something else wrong with it and rate of success on such repairs is very low. A whole new ice maker is much better idea.
- The ice maker
Part number: AP3182733 
Here are the breakdown diagram and
Replacement parts for WHIRLPOOL GD5RHAXNB00 | AppliancePartsPros.com
Gene.