In case you haven't solved your problem yet...
The door panel isn't hard to remove. Follow these instructions:
Removing Door Panels
I haven't had to track down window problems, but I can't imagine doing it without removing the door panel. As for the locks, they should be easy to install. They are only difficult to remove if you can't turn the key in the lock. The service manual should help here. I've done this a number of times on my 300SEL.