I recommend you to have a look at Blender (
www.blender.org).
I realy like working with it. I started learning with the wikibook "Blender 3D: Noob to Pro" wich wasn´t completed at that time. But it was already great to learn with it. It seems to be much more finished and very well formated. You can find it here:
http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_ProYou should even take a look at this page:
http://wiki.blender.org/index.php/Manual/ManualTo use it together with 3DGS it is best to use the .mdl exporter written by ventilator (thanks!

) you can find it here together with a tutorial (written by ventilator as well^^):
http://user.schule.at/go/blender/index.htmlAfter I learned the basics of Blender I liked modelling much more then before. It is a great and very powerfull tool.
Oh and you should definatly go on with modelling.