3d Landscape Design Programs

How do I get started learning 3D design?
I am a high school student and very interested in a career in 3D digital design and animation, specifically fantasy and virtual landscape design. I have no idea where to begin, and there are no classes in my area to help me along. Are there any beginner tutorials, programs, or online classes I could experiment with? Do any of you have any tips?
Do you know this one ? http://sketchup.google.com/
Landscape Design Software