Thermistor replacement
If you know the temperature characteristics of the new thermistor, then attach the instrument to a known resistance chosen to be in the operating range of the incubator and confirm that the indicated temperature is correct according to the nominal resistance of the new thermistor at that temperature. It should also read accurately at 25°C if the new thermistor matches the old one.
You can make up the test resistance with individual resistors and/or a pot if you don't have a resistance box on hand. Thermistors change resistance a lot with temperature so you don't even really need precision resistors, just measure the resistance with a reasonably accurate DMM to confirm.
I would be reluctant to invoke this 'automatic temperature calibration' unless I understood exactly what it is using for a reference and what it is adjusting.