Mark,
I did not realize that the problem was that severe..... it definitely has a bow in the root plane. Yes, that much sanding would require replacement of the root rib and recovering at that section.
Creek might have to replace the whole plane as I don't know how they are on spare parts stock. This model is out of stock until after the first of the year so you may have a wait. Hope you are able to contact them after the weekend. Their lack of response has me worried too.
PilotFrog