You can use sketchup to make models yes. However you will still need to know a bit of GMAX or Blender. as once you have built the model in ScketchUp Pro you will need to export it for GMAX, then finish it (textures, animations, attachments, etc) in GMAX. Then you can export it from GMAX into TRS. So yes you can; but you might as well just learn to use GMAX or Blender.
a side note; I would assume you could use Blender for the exporting and such instead of GMAX; I've never used blender so I cannot say for certain.
peter