I had a spinal tap, done in an ER setting, and it went much better than I would have thought. There was no pain involved at all, just a "funny bone" sensation shooting down one leg into the feet, and it only lasts for a second, at the very end of the procedure. Otherwise you'll feel next to nothing, the area will be fairly numb. If all goes well this is literally a 5 minute procedure. You should lie down afterwards and drink a soda with caffiene as well as some water, to prevent a headache. Good luck.