How do I turn the headlight off?

It's probably an LED if it's a recent model. Instead of cutting BOTH leads, just cut ONE leg of the diode and leave it in place - it's simpler to fix if you change your mind down the road. If it's a white LED, cut it completely off, leaving the leads to the LED as long as you can, and send it to me. ;)

Alternatively, if it uses a drop-in decoder, you could convert your railroad to DCC and turn them on and off whenever you like.

Well, yeah. That'd turn it off all right. Turnin' it back on agin could become a new problem.

Uncle Joe.

Make sure the ends of the snipped wires are >>

I suspect that most likely not. Just make sure that you tape over the cut ends to prevent any "unusual occurrences" from happenin' later on.

Uncle Joe

Doing some special-forces field model railroading?

Try using an IR headlight. Then you can see the train with your night vision goggles. :D