Do I need to open up the wall?

My upstairs toilet has leaked into the ceiling above the downstairs bath room, the leak itself is an easy fix, the situation is as follows. There was a lot of water and the better part of a 3’x4’ area of ceiling was completely soaked. To the point of the dry wall tape around the vent van and paper on the drywall slopping off when I removed the vent fan cover. (The leak was discovered by the water dripping out of the fan). The ceiling is slightly sloped toward the outside wall and you can tell by water pooling up under the paint that it has run down into the wall. The question: Do I need to remove all the drywall from the ceiling and wall clean it all out, replace the insulation etch. and close it back up? Or will letting it dry out, repair the surface and paint be sufficient? Its not really a matter of money that’s the issue it’s the time that is a problem.