Replacement is a very straightforward installation.
If you look at the case on top of your handlebar that holds the main button, you can see it has 2 screws to attach to the handlebar.
1) unscrew the top part of the case where the sticky button is in, lift it up and you see it has the PCB board inside (circuit board)
2) unscrew the 4 screws that hold the PCB board in place, no need to touch/loosen/undo any wiring
3) screw the PCB board onto the new top case and screw the new top case back on with the 2 screws.
Be careful to only use the included METRIC Allen keys and carefully unscrew the top case in order not to strip the screws.