replacing rockers

Some pictures of what your trying to repair might help. Auto Metal Direct sells the inner and outer rockers. You have to drill out all if the factory spot welds holding it to the floor and a and b pillars ,spring mounts,wheel wells.
You'll need a good mig welder, lots of free time and patience .
I wouldn't cut out anything you don't have to. Do it with the car sitting on its suspension. Use the door to line up the new parts.