Four countersunk machine screws hold the two metal brackets in place. Undo these, place them safely out of the way (having noted the size), and gently lift both brackets at the same time. You may have to turn the motor slightly by hand in order to do this, but please, no force.

The front bracket lifts off the motor spindle. Note the oval end to the spindle, which was possibly preventing the brackets from lifting out.

The rear bracket is held in by two smaller countersunk machine screws. These are tight. No need to take this bracket off unless you really need to. Note the orientation of the motor. The right angle part of the bracket is on the opposite side of the motor from the spring clip that keeps the brushes in place.

If you do take the bracket off, then it looks like this.

Brand new, pristine motor. (Ok, Ive run it a few times, but when I got it it was all sparkly). Look at the size of these carbon blocks. You don't often see them like this !

Once the motor is out, you will be able to lift out the bottom circuit board which provides the contacts between the motor and the wheel pickups. Be careful with this, the wires are thin and held on by solder. One side (the opposite side to that shown in the photo) has 3 fragile contact strips which can be damaged easily.

The photo shows the smaller circuit bottom side up. The side that you can see fits face down with the wires on the far side (RHS) of the loco as you look at this picture. The larger board is shown face up.