Disassembling this engine is pretty trivial. When you flip the engine over (on some soft padding), there are two small screws visible under each of the trucks. Swivel the truck left and right to gain access to the screws. This photo shows their location.
The grab bars (one on each side) have to be disconnected from the body for the body to be able to be lifted off of the frame. I use a small pair of thin tweezers to get in between it and the body to be able to pull it out. It is in there quite tight.
This is what the inside of the engine looks like. The shell remains connected via a plug near the front of the engine. The board to which the plug connects is held in place to the frame with two small screws. Once those are removed the entire collection of boards and the Tsunami decoder can be lifted away from the frame.