Have no experience with Corian rudders, but in general would expect a significant adjustment in price for such a substitution, especially in this buyer's market. Also, unless you're very boat savvy, I would have a surveyor or at least someone very knowledgable look at your pintles and gudgeons to make sure there's no structural damage being covered up with paint and filler.
Also give the motor mount a good scrutiny. I looked at a H23 that had a very loose motor mount similar to the one in your picture. The fact there's no motor and a fabricated rudder would raise a red flag in my mind, and prompt a marine surveyor's visit.
I would pay no heed to the anti-hunter comments. If you find a boat that is solid, a good fit for your needs/desires, and you enjoy it.....that's all that matters.