What needs to be done to fix this?

I'd run it by a body shop and they can tell you what it needs.

If it is metal, you may be dealing with metal fatigue if and when it is pounded back to the original shape. It also looks like some fiberglass damage. Is the center metal post broken off? That need to be a new one unless you can weld it and trust it. Like Bob said, take it to a body shop for an opinion on replacement and cost. You may have more damage than is showing in the picture. Get more that one body shop opinion also. Prices can differ a lot. Don't cut corners also.