I have a horror story for you. Mine was ordered by the first neuro I saw who ordered all of the expensive testing but did not share results with me. The day after my lumbar puncture, one leg was so weak that I could not walk on it. I called and left messages for the neuro but he couldn't be bothered. I learned on the internet that temporary paralysis can occur and hoped for the best. To this day, I have a weak leg that worsens during flare-ups as a result of my lumbar puncture.

I did not have any pain or problem at all with the lumbar puncture itself. BUT, I did get the headache that some get after it. The place that did it, did have me rest and lay flat for 1 hour after the procedure.
I had to go back and get a blood patch due to the extreme headache. I was told at Mayo (where I had it done) that it was usually women of menstruating age, that were most likely to get the headache. (that was me--yay).
and yes.....it was caffeine tablets that FINALLY got rid of it, that and laying flat.
good luck with the procedure.....as long as you don't end up with the dreaded headache, it isn't bad.