Best of luck on your surgery! I know it can be stressful the wait up to the event. While I don’t have any spells right off the top of my head, I am a huge fan of meditation and looked for a few pre-surgery specific ones for you that might help 
Oh actually I did find a post that might have a helpful spell - I think creating a sigil would be a great idea!
I know the anticipation and worry are almost worse than the surgery at times. Do your best to distract yourself, meditate and focus on positive things.
Make a good luck sigil
How to make a sigil 101