My GWP tore her CCL (Cranial Cruciate Ligament - the dog's version of the ACL) when she was approximately 5 years old. I decided to do surgery as she was entering her hunting prime and had a long period ahead of her for activity. We had a very successful outcome. Surgery was over the summer so I wasn't able to hunt her much that fall but did get her out shortly late in the season. By the next season she hunted great, with no issues. Her dock diving at the cabin did not seem to be impacted either! That being said, every dog and every surgery will be a bit different.
There are a few different methods for repairing the CCL and which one used will depend on the veterinarian as well as the dog. Some vets prefer different methods over others and some techniques are only appropriate for certain dogs based on size, structure, injury, etc. ECLS - Extracapsular Later Suture is the traditional technique, with a 'new' version of this procedure being referred to as the TightRope preocedure. I've seen many dogs over the years with ECLS repair do fine, but there are better ways these days especially for a hunting dog. The two newer approaches are TPLO - Tibial Plateau Leveling Osteotomy and TTA - Tibial Tuberosity Advancement (including a new version of the TTA called the MMP - Modified Maquet Procedure). Either of these two approaches would be preferred for a canine athlete or hunting dog. I strongly recommend that you have your veterinarian provide you an explanation of the pluses and minuses of each procedure as well as why he/she is recommending one over the other. If they only offer one procedure at your clinic and it doesn't match your expectations, you may want to consider going to a specialist location such as a vet school's teaching hospital at a university or a veterinary orthopedics center.
My dog had the TTA done and as I said it was very successful. She is now 12 years old and hunted well up through last season including multiple day hunts as well as the 1/2 day or day hunt. She's likely retired this year due to other issues but I was glad I got the additional 7 strong years hunting with a great friend, including seeing my son shoot his first pheasant over her last year.