I have downloaded all the appropriate tools, I think. I have a model of a (very large and detailed) building. I was told that I should rotate the whole model around the red axis before converting, so I did.
http://www.rigsofrods.com/wiki/pages/Sketchup_Tutorial
I ran the converter but its been running for several hours now. Should it take this long? Is there anything I can do to speed it up?