I am going to concentrate on the Front Bogie. The Rear Bogie is identical (almost).

Remove the cheese head screw, and lift the plate from the screw hole. It has two tags which slot into the near side of the loco.

And lift out the worm gear. WARNING. The end without the plastic has a small brass bush next to the worm gear. If you are not aware of it, it will drop off the axle while you are not looking.

The front worm gear also had a very thin washer. Although it has a hole, there is no room for it on the axle - it just slots between the larger bush and the chassis, to take up a little free play. Check whether yours has one of these, and don't lose it.

Looking inside at the rear axle of the front bogie. Note the little copper contact strip which transfers power from the right hand wheel to the small circuit board. This is how we know which end of the engine is the front. The positive pickups are always on the right. There are no negative pickups - power is transmitted through the metal body from the axles.

The rear of the loco, which I have marked in pencil with an R. Note the bulb and its clip. You may wish to remove these in case they get lost, but there is no need to pick this loco body up a great deal, so it is unlikely that they will go astray.

Although having said that, here is the front one making a bid for freedom.

And here is the workbench at this stage of the proceedings. I don't recommend leaving the little screws out like this though.