I purchased my 2018 used last September...only put 2500 miles on so far but it's mostly because of the kids sports...we are constantly carrying too much gear. Next 2 months it'll get used more as baseball breaks. Nothing wrong with having a play toy if you can afford to keep it.
I just sold...
I'm not near my car to take a picture but their website has a bunch of pictures that might help.
LED Sidemarkers for 2015-2022 Ford Mustang (pair) (diodedynamics.com)
The Diode Dynamics Clear Corners were maybe 2 minutes per side, super simple. Basically pop out old one, unplug, plug the new one in and put the lens back in.
2015-2020 Mustang LED Side Marker Light Rear Pair Installation - YouTube