Our Yorkie (we won't mention any names here
) was fixed when he was around 6 months old. It went fine. We made sure the vet had worked with smaller dogs before and that they were well aware of what they were doing. He got fixed and had teeth pulled out at the same time, so that they would only need to anesthesize him once. He was sort of sad for a day or so, and very groggy and down (not much activity, which is unlike him). However, he jumped back to normal after a day and a half or so, and was fine after that.
Neutering your boy is good for them, it can help them not run away when they smell a female in heat in your neighborhood. I think he became better with potty training after he was fixed as well. While I'm sure everyone emphasizes problems when getting neutered or fixed, just remember that most people do fix their Yorkies, and it's a good thing. Most will have no problems at all during the procedure.
