They put a large needle into your spinal column and remove some spinal fluid. It is uncomfortable, no denying that. But not shrieking from the ceiling bad. Like most things, because you don't know what to expect you think it's much worse than it is - during. The headache ranges from a mild sensation to something like a good sinus infection. The information they can get from that fluid is incredible... it's worth it.
Follow their directions exactly
and you'll recuperate much faster. Yes, do do have to stay down for a while. DO IT. They used to keep you in the hospital for a couple days to make sure. Now they usually let you go home.