No, what I am doing is suggesting things to make what you already have better. Some things like the trees right now don't require that much of an effort actually (top hit on google search fyi) and it will look much better. Other things like upping texture resolution is indeed more involved for less of an improvement, but that is indeed just my suggestion. I was also talking about just putting more details into it, ie put some different looking parts in the textures you already have to break up the monotony when they are mapped to large surfaces. About the lighting, I don't know how simply it can be done with Unity but again, this is just basically down to modifying values in engine to give the shadows more contrast so that not everything is lit up uniformly like it is right now. Finally, I suggest the terrain tool because while you can indeed control the polygon count with your 3D modeling, it's just much more impractical (in my opinion) than having a fully separate terrain you can remodel anytime with simple tools, not to mention texturing it will be a hell of a lot easier.
I hope you can see that I'm not asking you to rework the entire game, just improve certain things I feel are lacking right now compared to other things you already have in there.
More trees from the same guys:
http://www.turbosquid.com/3d-models/...el-tree/480769
http://www.turbosquid.com/3d-models/...ds-free/480746
http://www.turbosquid.com/3d-models/...ds-free/480774
http://www.turbosquid.com/3d-models/...d-model/480733
http://www.turbosquid.com/3d-models/...d-model/480700
Here. There's everything but deadzone adjustment and sensitivity. Analog will work so long as your prototype is properly recognized by the computer. You can adjust deadzone and sensitivity with Windows anyways I believe.