Matt, fristly welcome to the forum.
You dog is just a puppy, so to have this already diagnosed AT THIS STAGE is something you might wanna discuss here at a later stage re compensation etc...
I would second what Natty has said. A second opinion would be vital to me for reeasons that i won't get into yet as I'm too tired. Sorry. Lol.
Large/giant breeds with situations such as this can change dramatically as they physically mature, sometimes for the worse, and sometimes for the better.
If he was my dog, i would get another opinion, look at all options, and yes if need be, operate now with the hope of securing a favourabl outcome and results for your dog's future.
I'm so sorry this has occured for your dog. I really am.