Your 686 no dash is decades old. So it may not even have the lifetime warranty on it.
I would caution you to take extensive photos of it before sending it in to S&W, to document its current condition. That way, if it comes back to you with finish damage (which I consider a 50% probability) you will have proof that they caused it. Frankly, I would rather have a good gunsmith work on it than the factory repair folks. Your mileage my vary.