I am pretty sure that I took all the side walls (the ones that extend between the end panels) out prior to the end caps. In the front, I think I took end cap out after I took out the wall panels below the end cap. At least that's what my pictures show. All the walls around the front end cap had some thin aluminum trim that went between the end cap and the wall panels to give a nice finished edge. At the rear, the side walls came out first, then the end panel, then the end cap, then the panels that were below the end cap. No trim was used since the bath pieces cover the seams.
Here's what I know I can't remember: Of the top, middle, and lower side panels, which overlap which?