The installation is for HO-Scale Red Ball Trainmaster. It uses T1 decoder and was performed by Jean Lacroix.
This model is a brass import model. The body is attached with normally 8 screws located underneath the locomotive. There are 2 screws that retain the front truck bolster and 2 more for the rear truck bolster. Four (4) more screws are keeping the motor platform in place. Just removing all the screws will release the body free.
All the wires connected to the motor should be removed from it. The motor has to be unscrewed from its location since it could create an electrical short in dcc mode. To prevent that, install on the floor of the locomotive, where the motor was, a rubber pad or a piece of plastic tape large enough to isolate the motor from the frame.
The motor should be glued in place using Goo, double sided tape or silicone, taking care to avoid any moving parts. Pay special attention to align the drive shaft and the motor sprocket
The orange and grey wire from the T1 harness should be soldered to the terminals located on both side of the motor, at the top. Then connect the red wire to the top of the front truck the black wire that should be attached to the rear truck.
The decoder was installed on the ceiling of the locomotive body as shown in the picture.
The leds used for lighting were installed directly in front of the headlight holes. This has the advantage to prohibit wires to get entangled around moving parts of the drive train. You now have to reinstall the body and the screws that hold the body.