On Older 2 rail locos, one truck had the insulated wheels on one side, the other truck had them on the other side, and this evolved into have both trucks insulated from the chassis.
There is problably nothing wrong with the mechanism in that loco. There is no need to make it a dummy. You can find the short and that may fix all problems and it should be simple since it is in the wheels. Then reinstall the electronics. If the short did not burn them up, all is good. '
If the electronics don't work, just put in a new control board. I don't know about MTH boards, but you can get all sorts of options for control and/or sound for DCC. My favorite for motor control only is the NCE D408SR which can handle 4 amps continuously and has a stall rating of 10 amps. And the motor control is just great. Also it has 8 functions for lights smoke (which I don't like) and any other things or lights you might want to control.
