I haven't had time to repair mine yet, but I'm not gonna let the dealer fix it, I don't trust the quality of their work. I already cut out the weather stripping which seems to be holding the water in the flange, thus creating the damage. not a good design!

Next I will strip the paint and rust out of the groove, and then coat the bare metal with aluminized zinc coating, and then respray with etching primer.
After that I will be mixing a white pigment into West System epoxy and painting the area to completely seal off any stagnating water from condensation and to protect the overlapping metal from further corrosion.

It's an easy job, just time consuming, but it will look better than what the dealer thinks they can do with new parts.