There was already a small water-damaged spot on our ceiling in the master bedroom, so I cut a small hole there. When I turned the heater on, air came out of the hole I had just cut a lot harder than the vents. I climbed up there and figured out that our ducts were completely disconnected! I couldn't see down into where the disconnect was, so I stuck my camera over the edge, facing straight down, and this is what I saw (below.) All winter, all of our heat was blowing out of that duct and heating our attic!!
I couldn't reach that duct to pull it back up, so I found an old hook in the garage and taped it to a long metal cord. I used that to hook the duct and pull it back up. I drilled a couple holes in the duct and screwed it into the framework of the attic so it wouldn't get disconnected again, and then I used some metal tape (you're not supposed to use duct tape on ducts!) to seal it to the other duct. The only money I spent on this repair was buying the metal tape, and the AC/Heater company wanted to charge us over $2,000!
Next step was repairing the hole in our ceiling, which I had never done before. But it wasn't too difficult. I bought a small square of drywall, cut the hole even bigger so my square would fit, screwed drywall screws into the joists to hold it up.
Then my father-in-law got in town, and he helped me apply the drywall mud, and drywall tape, sand it down, and then apply texture from a texture can.
Below is the finished product. It doesn't look that great at the moment, but once we paint it you won't even be able to tell it was there.

