Depends on how much you're planning to etch, and how.
If you're gonna submerge the hilt, then yes, remove the electronics.
If you're doing a small spot on the hilt and hit it with a little cotton-stick, then just tape the rest and be careful.
Use common sence, electronics and water don't mix. Let alone a vinegar and salt mixture.
But thinking of it, I don't know how the electronics will react when you put a 9v battery on the hilt.....
If you're using any type of electrolysis etching, theoretically the electronics SHOULD be removed.