225 Engine Rusted Where Waterpump Mounts, Still Leaks After Replacing, What To Do?

My 225 has been leaking fluid like crazy so I took it in to a shop and have them look at it. Problem, bad waterpump. So now it's been replaced but it's still leaking. They are saying the engine is rusted/pitted where the gasket/waterpump mounts and they need to sand it down so it's flat and place another gasket to make up for the sanded down area. Does this sound right? I am a bit scared and thinking about taking it somewhere else. Please someone chime in on this issue as it's at the shop now and need to figure out if I should keep it there or go elsewhere? Thanks!