I have to agree Yorkie Daze. I've been down too many roads of going with my regular vet when specialty care was warranted. It cost me more heartache and money in the long run.
My dog Daisy was the same age as your dog when she had surgery on her grade 4 LP. she recovered rapidly and is now almost 10 years old and we've never had another problem with that knee again.
Others may disagree, but I believe that a specialist who has undergone board certification is far more qualified to do this surgery. This is not a routine matter, it is a speciality surgery. I would ask myself this -- would I let my general family doctor operate on my knee? No, I'd go to an orthopedist. I applied the same reasoning to my dog.