I went in person. The passport office at our Post Office is in a room by itself. There was no one else there. It wasn't an issue. I had my BC (not changed), my name change order, the passport application (new, my old passport expired decades ago and was lost), my top surgery letter, my driver's license (changed) and money. 🙂
If you only have 1 surgery letter, I'd bring a copy. I got all of my documents back except my letter.
Jay