There is an article on our club web site on how to add battery car MU plugs to a USA Trains GP38-2. The article included the following disassembly method.
REMOVING THE HOODS AND CAB
Remove the screws holding the coupler brackets and couplers to the frame. Set the couplers aside for now. Install the coupler bracket screws back in the frame.
Unplug the four wires from a motor block. Gently spread the side frame and slip one end of an axle from its bushing. Repeat for the other end. Repeat the process for the other axle and remove the motor block. Remove the excess black grease from the ends of the axles. Repeat the process for the other motor block. Set the motor blocks aside for now and wash the black grease from your hands.
Remove the two small screws (indicated by the yellow arrows) from the base of the fuel tank. Remove the fuel tank and set aside for now. Install the fuel tank screws back in the frame so they don’t get lost.
Remove the twelve long screws holding the hoods and cab to the frame. These are hidden in twelve deep holes. Four (circled in yellow) are inside the side frames under the long hood.
Four (circled in yellow) are under the fuel tank.
The last four (circled in yellow) are inside the side frames under the cab.
Lastly remove the four short screws (indicated by the yellow arrows) that hold the battery boxes to the frame. Their heads are not recessed.
Turn the locomotive over. Carefully lift the shell from the front of the long hood. The whole shell (long hood, cab, battery boxes and short hood) will lift off as one piece.
CAUTION: Do not lift the shell off too far or the wiring may unplug.
Install the four screws back in the battery boxes and the twelve screws back in the long and short hoods.
