I just got back from my local apple store and discovered the problem with my macbook pro is within the node structure of the b-tree. A disk repair attempt yeilded a notification that their exists an "invalid node structure". The apple support recommended I talk to "Data Savers" in order to rectify the problem without losing the ~319GB of priceless data I have not backed up. (I know i'm foolish for not being preemptive about such adversity) I'm hoping someone here can maybe give me some advice on the most financially feasible options for me to rebuild the b-tree and catalog i.e. anything i might be able to do on my own. thanks!