The IES DXF export is in 3D, not 2D. The slight problem you might have is that the free version of SketchUp 8 does not allow you to import DXF's. There are third part plugins that are supposed to allow this but I've never had much luck with them. I've found it easier to search for the SketchUp 7 installer on the Internet and install that alongside version 8. Version 7 CAN import DXF's so you can bring the IES geometry in via that, save, and then open in SketchUp 8.
The IES plugin will then handle the import for you (have a look on YouTube, there are lots of videos explaining how IES and SketchUp work together). It imports via XML I believe.
When exporting from IES there are a handful of options. You'll probably want to export it as "PolyFaceMesh with Openings"
Have another try, it's worth the effort it you get it working


