Hi Jim,
If your unit is correctly textured in Blender but solid grey in G3D Viewer this probably means you have not assigned a material and texture in Blender.
1. Add a material to your model.
2. Add a texture to the material.
3. Make the texture an image type and select your texture file (the image texture name is the property actually read by the python script).
4. Make sure your texture file is next to our model file when opening with G3D Viewer.