What model is your robot? You rather use a verification position just in case. For example if your tool has a flat surface you can use a level
Record a position and take note of the axis value at level position.
After motor replacement, verify that posture has not changed.
if there is a difference, level again and read the new axis value
From the new and old values you can adjust the calibration if needed
You can do the same for J4,J5,J6
Actually the technician should be responsible to return it to previous conditions.....