AT YOUR OWN RISK!!!!!!!!!!!!!!!!!!!!!1
What I did was....
With the unit plugged into the wall, install a empty AA Holder first
MAKE ABSOLUTELY SURE YOU INSTALL THE BATTERY IN THE PROPER DIRECTION!!!!!!!!!!!!

Installed 3.6v AA Battery and quickly cut Old Battery
Remove Old Battery
Install proper Battery from Mouser.com
MAKE ABSOLUTELY SURE YOU INSTALL THE BATTERY IN THE PROPER DIRECTION!!!!!!!!!!!!

Quickly removed AA battery
All that with your hear beating a Million timer per second, and sweating
Be very careful!