The early Oday 23's with the pop tops were notorius for being leaky. Given the state of the paint around the edges of the interior, I'd say this boat has/had that problem. It was a problem inherent in the design, so fixing it won't be easy. Also, check the centerboard. It is controlled by that crank on the table stand in the cabin. The early 23's had iron keels, which of course rusted like crazy. The centerboards of these boats often froze inside the rusting keels. It took a lot of maintenance to keep the mechanisms in working order. Later 23's did away with the pop tops completely and went to lead keels.
Broken mast? Yikes. I would stay away from that. Unless you are a skilled metal machinist, I don't think masts are repairable. Taking six inches off won't affect the boat too much. The biggest impact I can see is that unless the main was resewn, the shorter mast might mean that the boom swing will be below head height to someone seated in the cockpit. Not a good thing.
The short answer here is that there are a lot of boats in this price range and of this size, probably in better shape and better designs than this one.