 Roof shingles are actually pretty easy to disassemble if you know kind of a trick of the trade. I like to do it with a flat bar that you can slip up under the roof shingle, find the nail and sort of pry it from side to side and it'll pop right out. And then you replace that plumbing vent flashing and put it back together again and make sure you put everything in the right order so the roofing lays on top of the flashing. That usually stops that leak.