Unscrew the battery case and pull it out.

Make sure you have DISCHARGED the flash capacitor before. Now you could touch it and may get a electrical shock. It is rated for 315 V and 134µF.

Be careful again with the cable between the mainboard and the antenna.

Disconnect the ribbon cable, unscrew the flash PCB from the battery case and pull them apart. Finally, the mainboard (and therefore the antenna and battery) is separated from the rest.