No that was me.
The point about " .. any modelling program that imports .X files and then export to .Obj will do the job" though remains, a lot of the entities don't have .x files only .dbo, but even when you have the .x files it isn't always as simple as it should be.
For example I used a conversion tool to read the .x file for a simple building from one of the GG packs and convert to .3ds format, limported that to Blender, cut an opening in one wall for a window, so far so good. Made sure all the surfaces were triangulated and had no holes etc, exported back to .x from Blender, loaded GG and tested it out. Initially the model looked ok but at certain angle the wall would disappear. I believe that has something to do with my "normals" or something.
I am continuingly baffled by the 3d modelling worlds inability to make things just 'work', a model made by one tool and exported to some so-called 'standard' file format may or may not load into a different tool correctly, and what is worse it usually isn't obvious that it hasn't! When you add in the fact that to do anything meaningful you need a tool-chain approach , with different parts of the process being done in different tools, when the final object doesn't then work in GG it is not easy to determining where in the chain the problem occurred.
Been there, done that, got all the T-Shirts!