Hi shayne, 3DS and OBJ files are polygon mesh formats, where the object is made up of a bunch of little planar facets - that is a much different way to structure 3D model data than the NURBS surface method which MoI is set up to operate on.

You can export to a polygon format from MoI at which point MoI will dice up its smooth NURBS surface data into little facets, but it is not very easy to go from already existing facets back to smooth big surfaces.

See here for some previous discussion on this:
http://moi3d.com/forum/index.php?webtag=MOI&msg=5149.4

One method that you can test with is to use the OBJ to 3DM wireframe converter from here:
http://moi3d.com/wiki/Resources#Obj23dmWireframe_converter

That utility program is able to load an OBJ file and then convert each polygon into it into a closed polyline curve in a 3DM file. You can then load that wireframe 3DM file into MoI and select all the polylines and convert them to trimmed planes using Construct > Planar. But this method generates one little trimmed NURBS surface for every polygon in the original file - your result will not be a smooth object but one made up of a bunch of facets and it does not work very well if you have a high polygon count.

- Michael