Sammyjo, my lp shunt was installed Nov 1st of last year. The surgery was uneventful. Recovery was a breeze for me. I was in the hospital just overnight and even did a bit of driving later the following day, Pain was not bad, the only restrictions I had were light lifting, showers only - no baths until the stitches came out and take it easy for a couple of weeks. My throat was sore after the surgery from the tube, but I wasn't aware they had used one.
As far as laying flat after the surgery, you will probably still be groggy afterwards so you will not be getting up right away. My surgery was first thing in the morning, By evening I was up and walking around. No problem.
I know that the time before surgery is tough. It is the not knowing that makes it so scarey. I am sure that if you ask your surgeon, he/she will explain it all to you. It is an easy surgery for them.