While somebody might be able to create a script to do this [which would be nice] I don't really see the need. Blender [free] already has an excellent feature to do this [decimate] and can be done without needing to learn blender interface.
Work process like this:
export .obj from sketchup
import to blender
right click object to select, add decimate modifier
set to whatever level [say .25] and apply
export from blender as .3ds
import back into sketchup
I'm a huge fan of sketchup, but when there's a better tool for the job...
[dsarchs]
