The medical procedure applied to intersex people is called a s-x change.
I have heard of that. I also have heard that it's more common than people know.
Yes being interex is definitely more common than people think. Variations of intersex may involve genital ambiguitiy and different combinations of chromosomal genotype and sexual phenotype other than the common XY and X-X.(female)
It makes me wonder how many people were born intersex that I know. I wonder if perhaps they are even aware.
Yes those that are intersex may not even be aware but those that are may go to s-x reassignment therapy (another word for s-x change) and this is typically carried out on humans.
Do they ever perform intersex operations on nonhumans?
Not that i know of. I guess the last part was pretty unnecessary! S-x reassignment is the actual term i believe you are looking for though :) is is the medical aspect of gender transitioning. It includes modifying a person's characteristics to better suit a persons gender identity.
I think that is important. I can't imagine how difficult it would be to feel like you are in the wrong body.