If, like me, your version of Maya is not supported with a niftools plugin, I have a workaround to create a 3ds file that you can import into nifskope. You may or may not know, that newer versions of nifskope do not play well with OBJ.
All you have to do is export your model from Maya to OBJ and then use Google Sketchup or the open source program, Meshlab.
Import your OBJ, then export a 3ds.
Then follow the standard procedure of opening a retail nif in nifskope and then importing your 3ds to the desired NiTriShape.
For collision you will still have to use chunk merge, but after the first few times you use it and build up template nifs, it's not as bad as it first seems.