Hi There ...
I had a spinal tap last summer and is was actually very integral to the diagnostic process for MS (for me). My neuro performed the lumbar puncture and made sure I was curled up in a ball. He was very gentle and it was not bad -- he did need to readjust the needle a bit and get me to curl tighter -- that helped a lot by opening up the speces between the discs in the spine (a certain spot he needed to get the needle). The procedure was done in about 5 minutes (drip, drip, drip) and I thought of the analogy of a "maple tree" -- being tapped for syrup. Schmaltzy, but it worked for me.
I walked out of the hospital room with a bandaid on the spot. I made sure to move very gingerly and spend the day on the couch to try to avoid the spinal headache. No headache -- just a little tired because I spent so much time worrying about the procedure.
Do yourself a favor -- don't worry, get it done. It is really no big deal.
best wishes!