Excellent questions @Brad ! For the contact sensor, if you take the cover off you’ll see a small plastic square that locks the sensor to the mounting bracket. If you push that little square in, you can slide the sensor off the mounting bracket. The magnet for the sensor just clips on, so if you twist it to the side, it should pop off the bracket.
As for the Motion Detector, simply push in and slide off the bracket. Hope this helps! 