If your surgeons need a letter, the very safest thing you could possibly do is ask your surgeon exactly what the letter needs to say. That way some crucial piece of information isn't missing, going and messing everything up.
Just wondering, but in Australia can you have the sex on your legal documents changed without surgery, or left blank? I know not every country lets you but some do. Supposing you had a blank or male document, you could get Gynecomastia surgery, which is breast removal for men. That's what I had done. My surgeon even knew I was trans, but he processed it through that way since he's got lots of gynecomastia experience.