I agree with JE Custom. Check it before hand, but you should be fine just unscrewing the barrel and putting it back together. I'd clean all the factory gunk out of the threads before you put it back together though. Like JE Custom stated if your spindle through hole is big enough I'd leave the action attached if you can and just slip it back inside. I wrap a rag around the action and some masking tape to keep the rag in place. With my barrel fixture I just indicate the barrel bore in and cut the thread for the brake. If you do it this way some sort of support should be used to keep the barrel from whipping inside the spindle.