What's involved in replacing the crystal on a watch? I'm guessing it requires removing the movement from the case, somehow removing the existing crystal, and then cementing the new one in. Is there more to it than that?

I'm asking because several of my watches have crystals that either have no AR coating or have a coating that's really ineffective and it drives me crackers trying to position my wrist just so, so that I can actually read the damn watch in certain lighting conditions.

Anyone ever replaced a crystal? Is this something a normal human being can do or is it best left to trained craftspeople?