NEVER buy a game sight unseen. Get very good pictures to make a judgment call before making a long trip or shipping a game.
You might have been able to spot the rust prior to seeing it in person and negotiated a better price for the work you would need to do.
As for the stern leg protectors, I agree that these are an upgrade and are essential to keeping the legs from damaging the cab.
You should complete the job, enjoy the game, and lean from this experience.