[HardcoreZ28]

Depending on how widespread the rust is under the paint that's a common area to make patch panels for. There is no need to replace the whole quarter and disturb good factory sheet metal and weld in aftermarket junk that never fits right.

You'd probably be looking at $600-$1,000 depending on what's all there I'd bet. Could be more if it's a widespread problem.

If it's not completely rotted away, just pitted, you could half azz it. Grind it down and fill with fiberglass filler, then blend in paint. But that may last you a year or two only and would not be the right way to do the job.