Decided to try repair without removing the whole unit. After turning ice maker off,
1) remove plastic cover..squeeze and slide down
2) find tab on the left side of motor assembly, release it and slide motor assembly to the left to remove
3) replace sensor in foam housing and fit it to the new trey
4) fit oval tab on the new trey into oval slot in motor assembly. With thumb on the outside of motor assembly and fingers on ice trey bottom, you can hold it together in one hand.
5) guide the round stud on the back of trey into the round hole on the back of the unit, then line up motor assembly and slide it back in it's place
6) press the test( reset) button to make sure things work properly
7) replace cover