There is nothing wrong with the living will and power of attorney. This motivated you to get it and now you have it. Tell yourself you won't need it, but in the REMOTE chance you do, it's done. That should give you extra peace of mind.
I don't know anything about excision and revision -- sorry.
You might consider asking your family doctor for a mild tranquilizer just to help you through the next few weeks.
Try to be prepared and try to stay calm. We all have been there. My planned surgery helped me clean out my closets and donate 6 bags of clothing. I also threw away lots of junk because I didn't want my kids to have to do that in case I didn't come home.
Stay busy --- try to get the labs soon so you have less time to stress over it.