I'd then have 2 or 3 contractors come out to give you estimates to have the original roof repaired. If you want to save some $$$, first, let him give you a price. Then, ask how much you'd save to prime and paint the ceiling (and wall(s)) yourself. If you go this route, buy good paint from a Paint Retailer. The 'stuff' at the home centers, in my opinion, is not very good. The retailers will tell you what 'tools' you need. Before you do anything, get a price on doing the paint job yourself. Paint the whole ceiling; not just the 'bad spot'. Paint all the walls; not just the 'bad one'. Measure the room and take that info to the retailer. You may find it won't save you that much $$$ to paint the room yourself.