You really need a professional to give you a firsthand look. At best we can throw numbers around that have no comparison to the $$ amounts you will actual receive to fix it.
On that note, I would see if you can fix it instead of rebuild. Sometimes the hoops you need to jump through in your jurisdiction are to big of a hurdle. I lived in the center of a large town once, and it cost $5000 just to get a new garage approved with engineering plans and a new survey. That was because I wanted to start fresh and remove the old one.
Had I left one wall of the building intact I could have called it a repair and just paid the $400 building permit.
This is why you need someone local, search some Friends and find someone reputable.
Then please tell us how you made out.