now I'm going to include everything you need to do this. so you won't need any graphics program to do the tutorial.
So after going over this tut you should have a new GP7 ingame.
Programs you will need. any hexeditor, notepad or wordpad.
and nifskope.http://www.niftools.org/forum/viewtopic.php?t=973
This tutorial is made for users with maya, if you don't have maya (max) the export settings will be different, same if you have blender. now as the binding the skin and exporting is easy enough. I can do that for you if you want to do your own project. however I won't do animations. (but if you can just reuse say the animations already ingame you don't need me to do that anyway, this is what I did)
now this is a very rough draft. if you guys have problems with it ask questions and I will try and re explain to the best of my abilities.
also you will need akmads scenario manager to add the GP7 to a map.
this is the first tut I have ever wrote, be nice please

and here is the actual tut.
http://eilelwen.com/Railroads/tut/tutorial.htm