Gmax will work for modeling but you wont be able to get the model in the game.
Softimage XSI or 3D studio max are the only ones that will export a JK2 model.
character tutorial for 3d max (gmax should be similar)
http://www.bakaneko.com/howto/comput...er/page01.html
video tutorials from Ben Mathis (see Low Poly Character Series):
http://www.poopinmymouth.com/tutorial/tutorial.htm