Changing Default Autogen

I'm new to scenery design, and read quite a few posts on this subject. It's mind boggling, and the Autogen SDK isn't any easier either.My question; is there any way to change the default buildings/vegetation without having to change the underlying textures? I don't want to create photoreal textures - too time consuming I guess.I also note that the SDK can open up vegetation (AutogenDescriptions), Roof and Extrusions. But i'd like to add other objects, as shown in the Global Library - how do I do that?RT