If you have the real world location you should be able to geo-locate you SKP and then import the land-form including a mesh.
Then you can model building on top of that...
You'll need to add trees etc too...
You'll need v8 Pro to do this effectively...
There are several good tutorials out there - as a simple Google search will show - e.g. http://sketchup.google.com/support/bin/answer.py?answer=36241
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