I think you want more of a 3D modelling program to do most of this, unless you are strictly copying and pasting from other areas. Blender and Google SketchUp are both free 3D modellers. Most people who do IE areas seem to use 3DS Max, which isn't typically free, but has a free version for gaming Gmax.
I don't think I have TIME to do most of this in a 3D modeling program, though I've more or less resigned myself to that for certain indoor areas that should be more manageable on several levels. Really, I'm reusing whatever I can without breaking immersion or the feel I'm going for.