Deena seems to have covered all the options, but with Otis, our first Newf who didn't have a hip socket at all on one side, and severe HD on the other, the orthopedic surgeon did give us one very useful nugget of information. Dogs, like people, have very different pain tolerances and some dogs with very mild HD are truly 'Lionel Barrymore' and experience extreme discomfort and others with severe HD exhibit very little, if any, discomfort. That's why it's so important to watch your dog closely. If Thor seems to be fine, postpone any discussion of surgery as long as you can. Do all the preventative measures you can (raw, if that works, glucosomine and condroitin, etc.) and just know that you are dealing with a chronic problem...won't go away, but may be tolerable. Also, I think it's essential to go only to an orthopedic specialist...a t least for a consultation to get the very latest advice. University Vet. training centers are a great resource and could be at a reduced rate.
With Otis, we did a total hip replacement at a year since his femur was totally away from his pelvis and, after recovery, was great. We never did do his other side.
Good luck and keep us posted.