This is a how-to for removing the cabin side trim panels. I did it by trial and error, mostly error, since I could not find a description of the procedure anywhere. It is much simpler than it looks, and most of what you think you will have to do is unnecessary.
1. Remove the three plastic woodgrain panels. The two outer ones are glued on, and must be levered up gently with a paint scraper or similar. The central panel is glued to a black plastic panel that is held by 4 tabs, approximately shown in the picture. Gently lever the tabs out. You will see two horizontal lines of rivets revealed, holding a chrome-and-black plastic frame.
2. There is also a vertical line of rivets at the rear edge of the panel, covered by a white plastic strip that pops out from the bottom to reveal the rivets.
3. There is a line of carpet staples at the bottom that will need to be pulled out.
4. Drill out the top line of six panel rivets, but don't drill out the bottom line too, as I did. You can leave the plastic frame in place.
Note: On mine there was a single seventh rivet hidden behind the top center of the plastic frame (shown in blue on the picture). You should be able to feel it by sliding your scraper blade behind the plastic frame, and then drill through the plastic to drill out the rivet.
5. With the rivets drilled out, slightly pull out the panel at the bottom and lift the whole thing up. It's done. I did not need to completely remove mine, and I think that there are one or two rivets at the front that I did not attempt to access. It might just be another slide fit though, if you want to remove the whole panel completely.
6. When I reassembled mine, I drilled out the rivet holes for the top line and the rear vertical line of rivets with a 0.149" drill bit, then screwed in #8x3/4" stainless steel tapping screws. I did not replace the hidden rivet, which must just have been for location during factory assembly. The plastic panels and strip all still fitted, and now I can take it apart in future much more easily. I velcroed the outer small woodgrain panels on instead of gluing them, but the center panel pops back in.
Note: be careful not to unplug the complicated power seat switch connector, if you have this. Make sure that your power seat controls work before re-securing the panel. I also took the opportunity to fill the armrest portion with more insulation.
A final note: this job would be very difficult with the seats in place. There are four small nuts securing the seats to their plinth base, and it takes just a few minutes to remove them, and then the seats can be laid back gently to lie on their backs in the lower area behind. No need to unplug them, as the power cord is very long.