How to change battery in garage door keypad?
I found this page which stated:

The second oldest style keypads have a pin hole at the bottom of the keypad cover. You will have to insert a small Phillips screw driver into the small hole at the bottom of the cover and gently pull outward to loosen and slide the cover down to remove. Below is a picture you can reference.

But strangely, the picture didn't show how the screw driver was to be used.  I wasn't able to get this method to work.
However, I finally found that if I pushed in the center top of the cover I could create a gap wide enough for a normal flat head screwdriver to fit.  I then attempted to rotate the screwdriver to pry the cover away from the main body of the opener and finally heard a loud &quot;pop&quot; as the entire cover moved down about 1/8th of an inch.  I was then able with a bit of work to pry the cover off.  When I put the cover back on, I noticed that there was something of a lip on the top of the cover, meaning that the bottom wanted to swing in rather than simply go straight up.