
The biggest problem I find with looking up things like this on the internet is that many of the websites from vets recommending the surgery source information from their personal experiences, and many of those recommending alternative treatment either provide very few sources or do not cite their sources. Makes it difficult to figure out exactly how valid the information is.
I've known a couple of Goldens who have undergone the surgery successfully, though they were all +7 years old when it was done so can't speak from experience when it comes to a much younger dog. We opted for alternative treatment on one of my bitches, but she as 5 when it happened (the ligament just gave out while on a walk) and has strong enough supporting muscle that we only see the occasional hop. Her quality of life hasn't been reduced at all, but she could certainly never do agility or go back in the show ring.
The first thing you're going to want to do is get the swelling down in the knee and start gradually building muscle in the leg. This is important whether you do surgery or not, as recovery depends on strengthening surrounding muscles to support the joint. Unfortunately, there's really no way to tell what the long-term effects are of not doing surgery. Some dogs might be fine and live out healthy, normal lives. However without the Cruciate ligaments, the joint is less stable. After years of slipping slightly when the dog moves, it is possible for the joint to become quite damaged. The joint might look good now, and for the next few years, but what happens when your dog reaches 12 or 13?
Regardless of the treatment you choose, I would strongly recommend looking at hydrotherapy. It's a great way to build supporting muscle around the joint without the damaging effects of impact.