(http://www.swissquake.ch/chumbalum-soft/)
The Milkshape 3D modeler is named ms3d170.zip and is included in the Applications Folder. It is an excellent and easy to use 3D modeler.
There are no specific requirements needed to run the software (again, use the general guidelines mentioned above) but you will want a 3D video card such as a Geforce or Radeon to do 3D modeling.