steam sensor along with some of keypad not working?

evry once and a while (at least once a day) the microwave beeps and displays a msg which says ''steam sensor malfunctioning. Please service" How can I replace the sensor myself? 2. Some of the keypad doesn't work. Is THIS an easy fix? And last it will start up for no reason to cook vegetables!!!!!(it says so).
It is a GE over the range spacesaver