I just finished taking photos of how to do it. They'll be added to the User-Guide shortly. $3.49 was how much the battery (CR-2032) cost. A teeny-tiny (#0 size) jeweler screwdriver was the only tool needed. The entire process took just a minute. I had to do it twice though, as I made a discovery along the way and needed to confirm my hunch. Sure enough, Toyota provided a clever way of being able to easily check the status of the battery... or you can just wait until the car itself starts telling you (by beeping, flashing a warning, and not always responding). I didn't realize this feature was available, since I rarely ever actually see the thing while in use and it took 4.5 years for that battery to wear down. Anywho, press any button on the FOB and watch what happens. The mini red light in the upper-right corner will no longer illuminate if the battery is running low. Interesting, eh? .