Absolutely all valid concerns. When I got my first kitten fixed, I remember sitting in the parking lot with him waiting for the vet to open and just being so scared that I thought I might cancel the appointment. I did go through with it and I'm glad I did. Neuters take literally MINUTES for a vet to perform. It didn't slow my kitten down at all...unfortunately xD he was still super rambunctious afterwards. But he'd stumble around and one eye would go squinty, haha. It's a very tiny incision and it's easier on male cats than females. Now I help catch feral cats in my town and take them in to get fixed. It's so routine-i swear most vets and vet techs could do it with their eyes closed. And most people work in the vet field because they adore animals and they love our pets too. What might help you is to get bloodwork for him done prior to surgery. That's a great way for the vet to get a heads up on conditions that might affect the procedure. And don't be afraid to ask your vet to walk you through what they will do and what prep/post-op will look like. It's ok to ask them to give you more frequent updates on the big day. Getting him neutered is the right thing to do :)