Like Karilann, I've never had a spinal tap so I can't give you any advice. I do agree with Erika and Snoopy that it's too soon to worry about. You'll only work yourself up and create stress and anxiety. Also, if you are really nervous and anxious about the spinal tap, tell your neuro and ask if you can take something like a Xanax before they do the tap. It might help you stay calm during the procedure.
Good luck and let us know how it goes.