There was a thread about the windshield decal sometime back. You can only get 'A Daimler Benz Product' sitcker instead of the 'A Mercedes Benz Product' as original or something like that.
I'm not sure you can get all the engine decals. I know it's difficult to get in California the decal that says your car complies with California emissions requirements. They don't want to give it to just anyone. Maybe now that the gray market is a memory it's not a problem anymore.