Since owning my 40 and attempting to restore it I have noticed a few tricks to fixing it.
For instance if your door handle is on its way out your handle is more than likely fine. After yanking at mine and shearing off the handle I wssnt very happy. Connecting the outside handle to the inner door lock is a small rod with 2 hooks and a thread. When you pull your jandle the rod lifts the lock and opens the door. Over time this unthreads which makes the rod longer and unable to unlock the door. By twisting it tight you can save a lot of long term hassle. The rods also tend to bend and replacing the rod will almost certainly fix your door.