Traduzindo o passo 40
Three screws (red circles, shown here already removed) hold the ring surrounding the rear lens element.
With the ring removed, you can gently lift up the spring mounted rear element (yellow circle) with tweezers. I was then able to clean out the offending dust on the back of the element.
Time to reassemble everything (again!) - this time, everything worked fine AND no more dust spots in the images. Success!