You can change the battery by opening up the GPS.
Remove 4 rubber caps covering each screw by inserting the screwdriver into the side of cap and prying back and forth.
Remove the 4 screws holding the cover in place using a Philips #00 screwdriver.
Open the back cover.
Disconnect the speaker from the terminal.
Disconnect the battery connector from the circuit board.
Pry the battery off the circuit board. The adhesive attaching it shouldn't require any other tools.