Try not to worry too much.

Neutering a dog is much less invasive than a spay. And problems with spays are very few and far between.
I've had the opportunity to watch both operations when I worked at a vet.

Elvis will be fine and it really is better for him to be neutered. I'm not sure if he will become more loving etc, I don't really believe it affects a dog's personality that much.

The pics are great and he has really grown up into a nice little schnauzer.

Good luck we'll be thinking of you.