try the _OBJ import by Max Smirnov
http://moi.maxsm.net/media/files/ (scroll down)

But not take file of millions of Polygons!
Make some decimate before!

Nurbs are not like polygons! Very difficult to transform polygons in Nurbs! (better if you have only quadrangular polygons objects)

You can use after some tricky scripts of Max Smirnov if you want to rest in polygon SubDivision modeling inside Moi!
SubDiv(beta 9), SSPlit, SBridge, SSCale...