Yes, it is a valid concern, but a normal expectation of planking on wooden yachts. Contrary to what Zeehag has said, it is a great concern about the mixing of fastener metals, especially under the LWL. Your first concern should be to remove the steel
. This doesn't have to be done immediately, but don't go more then a couple of years or you can expect considerable degradation. I've been restoring boats for a number of decades and if there was one thing I could tell all wooden boat owners, it's get the iron out of their boat, particularly their planking fasteners.
The best way to get an idea of a refastening job is to count your planks and your frames. Then consider at least two fasteners per frame. The labor can be reduced considerably with your help.
There are a number of wholesale outlets around that carry fasteners for a bunch less then retail as Zeehag has pointed out. No one should be chased off by West Marine