If I understand you correctly you need to detach the parts as elements....unwrap individually and then attach those parts back together (assuming that you want them to be in same uv tile) and then repack that tile back together. By the way if you subdived after a uv map your gonna be in a whole world of pain! As far as I'm aware you should always uv map after subdividing. Depending on you topology it can and usually does causes stretching and overlaps. You should head over and search for Arrimus 3d on the Youtube...the man is a fountain of knowledge for all things 3ds max!