A nice shot of this D27 engine. There are two grey screws at the top. Make sure you have the correct size screwdriver, a slip here will make the grey painted heads become very visible.  Remove the screws, and place them in a container. Carefully lift off the plastic body. There is nothing to force, but don't squeeze the sides. Lift front and rear evenly.

But which is the front ? Well now, you should be able to tell. There are two wires connecting this circuit board to another board under the motor. Make sure that these two wires are at the side facing away from you. Front is then on the left. Put the loco on white paper, and mark F and R (front and rear) Also, pencil it on the metal body and on the circuit board. It helps.