HRM Battery Replacement

I've been using my Garmin 1000 on my bicycle for a couple of years.  It appears that the battery in the HRM sensor has finally worn out.  That would normally not be a problem except to replace the battery (a CR2032), I need to remove four tiny Phillips head screws from the back.  I've tried to do that but they won't budge.  Have other people had this problem?  Will I have to go to Garmin and purchase a new sensor?