Alternatively you can use a ruby exporter plugin for regular SketchUp that can export in DirectX (.x) text files. SketchUp models into DirectX XNA games http://edecadoudal.googlepages.com/sketchupwithdirectx Plugin code can be found here : http://edecadoudal.googlepages.com/xExporter.rb It supports textures and back faces.

Take a look at this previous article if it matches your needs. It is not an XNA Importer but a Sketchup exporter for DirectX (.x) file. http://forums.xna.com/post/47791.aspx It's a plugin written in GoogleSketchup Ruby API that is loaded when Sketchup starts. A new Menu is set in Plugins > ''Export DirectX ...

I also spent a lot of time on the Internet for any conversion software or tool from skp to directX (.x) format. If you prefer using SketchUp free, I start writing a DirectX exporter that can be found here : http://edecadoudal.googlepages.com/xExporter.rb