Usually there is some type of bulkhead / support under the main beams to transfer the loads from the beam / rig to the hulls. If you want to see inside the hull of the SuperCat take a look here http://themanshed.net/archived-projects/supercat-20/?g2_page=1 This is taken in my shop.
Back in the day I use to go to Bill's shop and see what he was working on when he was still building the boats and molds in Palm Beach County. Basically anything can be fixed but you have weigh the cost vs the price vs the time. If you have the time, skill or the willing to learn, and place to work on it is not too bad of a job. Although repair work is not as easy as an experienced person makes it look. I enjoy it but I’ve also restored old cars in the past and find it a way to spend some time when not sailing.
The other option is if you are paying somebody to do the work keep in mind time vs work = profit. Make sure they do it correctly and not just make it look pretty. It may be cheaper to replace the hull with a used hull. Like cyberspeed says did the mast take it out or failure of the hull? Make sure you check the other hull out before you go back on the water.
Good Luck!