Help with creating high poly earth

I need to make a high pily earth model for a game of mine. I will be actually walking around the earth so i need to make it as detailed as possible . So to do this i need to know how to use a bumpmap of the earth and apply it to my sphere. I am preety new with blender so im not sure how do so. i dont need it to be like 100% detailed ( i know it isnt possible) but id like canada where its supposed to be and china where its supposed to be ect… I also need to make the terrain textured. So can somone please guide me in the direction i need to go?

Before I go into detail of describing how to do what you want, let me ask you:
Is this similar to what you want?

Do you want a textured sphere that will be scaled to the Earth’s actual size in relation with your character?

And do you want geography (like mountains) on the earth to actually stick up, out of the flat land? For this you want to displace the mesh, not bumpmap.

Or do you want something more like this?
(image from Blender 3D: Noob to Pro/Landscape Modeling I: Basic Terrain)