Complete the terrain (materials/textures), and lighting for my map on Unreal Engine

I used a custom height map to bring in a new large scale map. I set it up for the most part how I want it (maybe even out the beaches, but good aside from that). I would need someone who is knowledgable about textures and materials to finish setting up this island. It is already surrounded by water but needs the coast covered with beachy sand, tall yellow grass outside the beach, and green grass in the wooded section, woods with trees and bushes, and an open section of dead grass. The lighting aspect will be dark, very dark. This will be a scary game that will be nearly pitch black outside of the users flashlight, firelight where that is necessary, broken lights in the house I will build, etc. So I would need a cloudy night sky with a moon behind the clouds. Please let me know how long it would take and what your cost for doing this will be.