not sure if this will be of much help. I have used sketchup for CNC work and some of the plugins such as stl or dxf converters are good such as the one here
[url]
http://www.guitar-list.com/.../convert-sketchup-skp-files-dxf-or-stl
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but i also use mesh lab software. I only use this for smallish models and prototypes so I am not sure how well it will work for you but try it
http://meshlab.sourceforge.net/
exporting from sketchup as a collada file and them messing about with it in meshlab, it does seem to work but needs experimenting with depending on what you are doing