There are many times in our lives that we face things over which we have no control; this is one of those times for you. I have not had the type of surgery that you describe, but I have had a total knee replacement. Was I concerned? You bet! I knew, however, that I could not go on living with the pain that I had and so told myself that this had to be. Am I glad I did it? You bet. My life has been ever so much better. I don't even remember that I did have it except for looking at the mark going down my left knee. Wish I had done it sooner.
You, too, will feel so much better when it's over. Just try to relax, stay calm, say your prayers, and it will soon be over.