A new area cover over the old front cab over window area is so much easier than replacing the full width front skin which involves removing the preformed corner molding which is so hard to keep from bending or kinking because the caulk under it has usually become like a glue thanks to years of the Sun's heat. Once you bend that molding even by accident, it will never look right again or seal properly and you'll expose all the screw holes to new leaks.
That's why I have always replaced all exterior screws that weren't already stainless to stainless and almost always 1/4" longer so they have some new bite. Steel screws almost always rust from the condensation moisture contained in the wood and or the difference in interior and exterior temperatures. Many times the existing steel screws will even breakoff and leave the rusting/rusted debris in the screw hole so a new screw even won't go back in. Just think about the rot that's around that rusted screw?
BTW, steel screws in aluminum and with ambient moisture/humidity which contains natural air born chemicals and pollutants is actually a small battery and over time the aluminum becomes sacrificed. No more grip!