If this is your first spoke I would just replace it and keep an eye on the wheel but if you are seeing corrosion then there might be other compromising factors and you might want to replace the wheels. I wouldn't go through the labor of rebuilding those wheels as they are probably low cost machine built jobbers and nothing really to write home about. Maybe a little more decent than the absolute bottom end but nothing high end enough to really want to spend the time and money to rebuild unless just looking for a project and learning experience but then I would just build a new wheel and use the old wheel to tear apart and not care so much about.