Well as for the skinning itself, I've almost totally figured out how the odasl.dll skinning system works for OP2. I just have to test it to see if I can get it to work on my own program.
So you could just use the odasl.dll + a cut down version of op2shres.dll (all you need is the skin bitmaps, etc. Or you could possibly compile those into your own program)
Well, to suggest the layout: You should post a list of what types of windows are needed.