11-08-2014, 08:55 PM
As you already have your object uv mapped and textured you can just use File->Load image to load the normal image into Wings3d, then in the Outline window you select that image and drag and drop it over the material which it should be assigned. You will be prompt about the kind of map you want make this assignment - choose Normal map.
I believe it should be exported as you expect.
I believe it should be exported as you expect.