Hi Runel
The reverse light switch is on the transmission next to the gearbox black end cover. Whatever you do don't take gearbox cover off. It is behind the end cover bottom right. Might be bit tricky to get out, jack the car might help securing on axle stands. There might also be a cable tie securing the reverse switch wire. When you unplug switch either put a rag in hole to collect possible leak or container and top up oil if necessary. when fitting new reverse light switch it is recommended to use thread locking compound on screw or bolt like loctite