This is what I did:
Replaced the nut retaining plates, they are cheap.
Wire brush the latch to rid the loose rust, neutralize it with POR or something similar, then paint it.
When re-assembling, make a gasket from pond liner or hot-tub liner to separate the retaining plates from the door. You may want to get new door latch gaskets as well, they are cheap.
Also, check the door latch cavitiy, odds are it is starting to rust as well as it is made from steel.
Spray Waxoyl 120-4 in the door latch cavitiy where it meets the aluminum panel and let it wick into the seams.