1. Yes, forgers will forge items.
2. Blender is free and can export to obj.
3. At the moment you just have to use the 'obj load derp.obj' command ingame to load the 3d part. For blender you should export with Z up Y forward, export the normals, vertexes, faces and triangulate the mesh.
4. In the future users probably won't get to upload their own parts, but if so then probably like textures.
5. Well currently you can move the object to any part using the command, eg 'obj load derp.obj 0 0' will put derp.obj on tori's head, where as 'obj load derp.obj 0 1' will put it on his right shoulder (if I remember correctly).