I ordered the replacement Spray arm and mount, received them Saturday ahead of schedule, and had them installed and working within 5 minutes. The one thing I did different than in the video, because I was replacing both parts, is to attach the supply tube and spray arm to the mount assembly before clipping the mount assembly into the rack. The screw fits very tight the first time, and it would have been much more difficult to screw it in with the mount in place.
I highly recommend replacing the mount assembly when replacing the spray arm and supply tube. If the arm or tube is brittle, so will the mount probably be. Mine broke with very little force, so I'm glad I had already ordered a replacement.