Trust me, you will only sip because of fear!  I gulped yesterday without thinking and the immediate discomfort and gas reminded me real quick!  I think one or two gulps won't kill you , but it's hard on the new pouch and can damage it if done too much.

The gas was pretty horrible, but I got up and started walking the halls the day of surgery and it is the only thing that helps. Believe it or not but most of my "gas" pains were in my left shoulder and they were quite awful. 

I was able to take a shower the next day after surgery, it was like heaven!  I had lap RNY and there was very little pain.  Just moderate discomfort unless I strained myself or wasn't careful getting in and out of the hospital bed. My bed at home is quite high and much easier to get in/out of.

Good luck, it will be here before you know it and then you will wake up and it will be over. Then you will start the mantra, sleep, pee, walk the halls, sip, sip, sip, and repeat...