It is quite a difficult operation as you need to remove everything else to get at the top-plate screws if I remember correctly. If you decide to tackle it, remember that the screw heads are JIS, not Phillips or Pozidriv. If you try to use the wrong screwdriver, you will certainly strip some heads.
Much appreciated Merco_61, I'll have to do a bit more research in what to look for when I get inside the D1 before get the JIS set out.