M.F.
Not the same surgery, but my son had surgery at 6 months for an undescended testicle due to a hernia. We were also going to circumcise him at the same time, but my gut was screaming "no" about that, so we called it off that morning. Once we made that change, I was much more calm about the whole surgery idea. He did great and you never would have guessed he had an operation an hour after it was over. I nursed him as soon as he woke from anesthesia, we brought him home and gave him his pain meds, just in case for the first 2 days, but as far as he was concerned, he might as well have been at the park that morning.
Try to stay calm and trust that he'll be ok.
Good luck!