I just replaced the door speakers in my 87 recently and did not need to
remove the entire door panel.  I (gently*) pried the panel area closest to
the speakers out far enough to grab and hold the plastic retaining ring while
I turned the speaker to remove it.  *There is a trim removal tool that
minimizes the chances of tearing the fabric and scratching the paint, but I
just used a screwdriver. Once the new speakers were installed I simply
pressed the door panel back into place.  (I noticed that the door speakers on
my 90 are different and are held in place by screws)  Hope this helps.
-Loretta
87 Syncro
90 GL