Welcome to the forum!
Turn the locomotive upside down and twist the trucks so you can see the frame ends.
One end will have a screw to remove. Once the screw is out, turn the loco right side up and pull up on the end of the cab where you just took the screw out of and pull it up slightly. As you do so, pull the cab to the back of the loco to unlock the rear of the cab from a tab in the frame. Pull the cab straight up and it's off.
The bulbs are #161-300
Larry