It is very natural to feel anxious when you are having a medical procedure. I'd worry about you, if you were not worried at all!
You need to remember that procedures like gallbaldder removal have been done for many many many many years so the docs have lots of scientific technology to draw upon so that it is now a routine procedure. Of course, it is not routine for you though!!!
Try to think of all the experience that the doctors and nurses have and how well they will take care of you. Take some deep breaths, close your eyes, and try to relax.
I'm a nurse and although there is always a risk to any type of surgery, this type of surgery is very routine these days. You need to think about how much it will help you to be calm and how when you are calm, your stress hormones are minimized - when stress is minimized, then healing is maximized.
Another thing to think about though, is that a little bit of stress is good - it's called eustress (eu = good) and good stress helps us to get prepared for things that will happen. Good stress keeps us vigilant and you must be vigiliant also, watching the things going on around you before the surgery - be sure things look right and comfortable. Ask LOTS of questions - get all your answers.
Good luck - I think everything will be just fine - it is perfectly normal to feel anxious!