Do some searching here on YT.....there are plenty of threads about luxating patellas. You can also do some reading online and get yourself acquainted with the condition. This will help you ask the appropriate questions for either your Vet or the Orthopaedic Surgeon.
In the meantime, I would call back your Vet and see what "grade" he gave your dog. You'll quickly learn alot and be able to make an informed decision.
You also might want to look into adding a glucosamine/chondroitin supplement to help with the discomfort. I use Cosequin and can find it relatively inexpensive online.
My maltese just had both his knees fixed....one in April and the other in June. He is doing wonderful.....
