I have one of those little POS cars. They are the perfect car to hang signs on as they grab attention everywhere they go. That aside the body panels are as you know, plastic... very soft and scratch very easily.
I had static cling graphics on mine for just under a year and the sides that got the most daily sun developed small dark spots under the cling. The dark spots mostly cleaned/polished off but several were deep into the plastic. My yellow plastic panels are solid yellow, no paint. Some of the spots were under the printed image and some under the clear.
I'm not going to be much help getting the panel off, I didn't take mine off as my graphics were small not a wrap also my car is the Cabriolet so the tail gate is different anyway. Mine does have a screw on each side and 4 across the top inside the inner rear panel that look like they could hold the outer color panel on. This car has storage inside the inner panel for the Cab rails... like I said it is different. Good luck.