Thank you! This worked perfectly although in the end I didn't have to bend the tabs. I've had the train for less than a week and hadn't noticed that the motor was not in the shell properly - when placed on a flat surface the locomotive tilted slightly to one side. When I attempted to straighten one of the tabs, the motor snapped into place and was able to then be removed as you describe above: it slid to disengage the slots in the front, and I was then able to remove it with the bent slots coming out through the battery portal.
Upon removal I could see that the motor is filthy with dust, hairs, some corrosion and general gunk. So, the cleaning process has begun.
Again, thank you for your help.
