Poor pup. I don't have any with this but I have had a young do go through surgery. One of our dogs jumped out of a car window and hurt him self bad. He was suppose to be on crate rest and the puppy sitter let him out front to go potty with no leash on. He took off after a cat and broke his back leg, witch had to be fused back together. If you can I would stay with the dog until they put him under, they get scared and confused when they get the anestesia. Also I'd see if they can give him anything other than morphine after the surgery. My dog had terrible withdraws from it and acted like he was is more pain than he should be, also it made him not want to eat and he dropped weight fast.
I'm very sorry about your dog, and I wish you both the best of luck. If you have more questions don't hesatate to ask.