Do you have welding and fab experience? I wouldn't consider replacing the rocker to be easy, probably not a good first job, but doable if you're smart. Look really hard at the inside of the rocker, especially at the front and rear, you might find something that is not visible from the outside, or from a quick inspection. Additionally, if you do go through with a full rocker replacement, be aware that the replacement panel, due to how it is formed and what I imagine is a less than perfect die, tends to have a split at the crease in the rocker where the front fender meets the rocker, and this will need to be welded up.
Tabco panels aren't very good, so as a general rule of thumb, if you don't need to use it, don't.