With the recent storm i have a 4' sq section of my roof that is sagging. It let water into the house. I know how to replace the drywall & re popcorn the ceiling. What i don't know is if it is safe to cut out the bad part of the roof. I would replace the plywood, seal edges, felt it then new shingles. I have lived here almost 11 years and it already had 3 layers on when i bought. I would need to add 3 to get the same level. Any hint would help so I dont cause any more dammage. Can't afford hiring it out as i was just released from my welding job. Know off any jobs out their im all ears.