maintainance

Hi! I just got my Range Rover two days ago. The previous owner had a house by the sea and when I open the hood there is a lot of sand in there, just resting on the surface of the engine and the car's body under the hood. I was wondering how one should cleanup that area? I can't just hose it down...

Any idea how can I maintain clean plastic or how to clean it? I live in a dusty area. The plastic come if you select same color roof rather than contrast.