They are right on the noise thing, helical cut gears will be noisy if they aren't broken in together. On the breakage, they might be just covering their butts and wanting to make a sale. I would try to get it off and if it comes off easily re-use it and if it takes excessive heat or force then get a new set. If you have a fry-daddy or a deep pot and a hot plate you can fill it with mineral oil, heat the oil to 350 degrees or so, and then dip the whole gear and cam shaft end in there to heat it. That will keep the aluminum from getting overheated. Just make sure to wear heavy gloves and long sleeves so you don't get burned by the oil. It's also a good way to heat it for installation because ovens tend to have hot spots.
