Undo the six screws holding the gearbox together.

An impact screwdriver will make this task much easier. With a normal screwdriver, the screw heads are likely to strip, meaning you will need to drill them out.

Lift off the gearbox end cover.

Lift out the gearbox centre web complete with the gear cluster.

Retrieve the two selector forks from the gear cluster (otherwise they'll fall off).

Retrieve the detent plunger and spring from the main casing (otherwise it will fall out later).