If that "somewhat bowed" panel needs a replacement, it has to be a sheet of exactly same pattern, and with the S-lock on the upper edge. These corrugated aluminum sheets are normally 2 or 3 ft wide, and can be 10 or 15 ft long. In big cities NOB you won't normally find more than a couple of shops with such a supply within 50 miles radius, this isn't something that an autobody shop would carry. A body shop could try and straighten it instead of replacing, but when somewhat straightened, it may still look somewhat damaged.
Storage lid is a trifle for anybody who knows fiberglass works.
The entire coach fiberglass laminate siding can be repaired in any boating shop, but damaged corrugated aluminum sheets need to be replaced with sheets of the same pattern, this is the only way to restore the original looks. Not that I care for looks when trailer is old.