If it helps, with regards to preparing them for GG when using Blender;
I've found that if you work with your units as imperial - inches, then when you export to FBX change the "apply units" drop down to "All Local" and tick the "Apply Transforms" box and the "Apply Scale" box, they import into gameguru classic at the correct scale and rotation as each GG unit is an inch (this doesn't work so well in Max as the scale appears to be different and i havent worked it out yet).
Also for textures to automatically detect in the GG importer, make sure you have a material assigned to the object, but don't put anything in that material and make sure the material is named the same as the name you are using to export. Also, mke sure your texture names are the same as your model, i.e. if your model is called pink_womble.fbx then make sure the material is named pink_womble in Blender, and your textures are called; pink_womble_color, pink_womble_normal and so on.
I usually find that if you set your models up like that they mostly come in fine in GG classic's importer.
As an additional step i've started to name my objects and the mesh data the same as my model, so if my model is three object, i will name both the objects and the mesh data as pink_womble_1 pink_womble_2 and pink_womble_3, i don't know if it helps but it gives me piece of mind and keeps things tidy
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