My GSD mix was diagnosed with HD and under a year old as well, and she had her surgery at just over a year old. Her surgery was a total hip replacement. We took her to Ohio State University to have the surgery. It cost about $4000.
Niko: American Showline GSD 4 1/2 years old
Rosa: American Muppet Dog (GSD/Border Collie mix) 5 years old