1) Remove and set aside the coupler assemblies.
2) Remove the nose, cab and long hood assembly by gently lifting the body from the walkway and chassis assembly. There are small clips holding the nose and long hood to the walkway, which need to be manipulated as the body is removed.
3) With the body removed, remove the screws which fix the chassis to the plastic walkway. Move all wiring out of the way so the chassis can be removed for rework.
4) Remove material from the chassis to accommodate the 20x40mm speaker and decoder.
5) Reassemble the chassis to the plastic walkway.
6) Hardwire the bogie pickups to the red and black decoder wires and motor terminals to the orange and grey decoder wires.
7) Hardwire the decoder's yellow (-ve), white (-ve) and blue (common +ve) to 1.8mm or 3mm warm white LEDs for the headlights. Yellow is the #1 end, white the #2 'long hood' end. Use 470-1000 ohm resistors in series with both the yellow and white decoder wires.
8) Solder 50mm long wires to the speaker solder pads. Mount the speaker under the radiator fans with the speaker face pointing down. Fabricate triangular baffles to seal the speaker in place. The sound enclosure should be air tight.
9) Solder the decoder's brown speaker wires to the 50mm long speaker wires. Correct heatshrink should be used on all joints to eliminate the possibility of shorts.
10) Check operation, direction of lights and motor relative to DCC cab direction. Use Kapton tape or similar to fix wiring in place.
11) Push body all the way home over chassis and refit couplers