From my viewpoint you have 3 options:
1) Finish taking out the bracket on your own and take it to a welding shop. If it is cast alumium they can Heli-arc weld it - it can be fixed.
2) have a garage take the bracket out for you and you then take it to the welding shop for repair.
3) get some good quality allen head sockets, a small screwdriver, a hammer and a 24" 1/2" breaker bar. Go back to the bones yard and clean the head of the bolt out with the small screwdriver, then hit the socket into head so it is well seated with hammer and apply the breaker bar. Then put the new bracket into your car.
Sometimes the stupidest thing on a car can take hours - ask me - I know!!!!