I need advice on my totalled yet still beautiful baby.

Is there a reason you don't pull it back into the barn so it doesn't get any wetter? The situation is probably beyond your skill set to fix but the damage, as it is now, can be fixed. In fact, since the only thing damaged is the frame of the pin box and the small area in the bedroom, it isn't an incredibly difficult restoration. Unless I'm missing something, $20K estimate is way off the mark.