Forgot to mention that you'll need to unscrew a few things before doing anything else on the door panels: the arm rests have two #3 phillips head screws, the chrome pieces surrounding the lock mechanism, and the unlatching lever has a small phillips screw underneath the black plastic liner behind the latch. Carefully pry the plastic liner out with a small flat blade screw driver to reveal the phillips head screw.
Also, there is a plastic liner between the panel and the metal part of the door - this is a moisture barrier and needs to be in place. If damaged, either fix with tape or make a replacement out of a large trash bag. Otherwise, water will ruin the door panel.
Here at FastLane you can order the diaphragms and maybe the tool. My tool is Snap-On, but you may be able to find one at a local auto parts store (NAPA has lots of tools, Pep Boys, Auto Zone, O'Reillys, etc.), make some calls to find one.
America: Land of the Free!
1977 300D: 300,000+ miles
American Honda: Factory Trained Technician & Honor Grad.
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.