need advise on body work

I'm getting ready to make a mess out of my '87 300SDL. It has some rust problems that I want to address before the onset of the Fall. I've figured out how to remove the lower plastic panels from the body
without breaking too many clips. Is there a way of removing the panel that extends from the rear bumper to the wheel well with out having to remove the entire rear bumper? My plan is to remove the rock guard panels and the lower door panels then grind out the rust, treat with POR and fiberglass as needed. This won't look pretty, but should extend the life of the car several more years. I have the colour matched top coat paint on hand for when the POR has cured.
In the FWIW category, the beast just turned 300,000 miles and rides/handles like a dream. Fuel economy is 28-29mpg and the AC will freeze you to death (while reducing the mpg figure by 1-3 mpg). I am delighted with the car and regret not getting a MB earlier.
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