You don’t need to open the unit. You really don’t. But since I know you are going to anyway, I’d rather you know how to do it without breaking it, so here goes.
The back cover (the one with the USB port) slides upwards. Keep it parallel and be gentle!
Once the back cover is off, unclip the button cap, then slide the top cover forward over the button. Again keep it parallel as you slide it.
The switch PCB is mounted vertically in the case, lift that straight upwards and out of the case.
Finally, slide the main PCB out the back side (away from the switch side).