dude, you can't replace the rear quarter yourself. This requires some major body shop work. Your car is unibody construction. Meaning the majority of the car is one solid unit. To replace the rear quarter, the original one needs to be cut out first and the new one welded back in. You are looking at around 8k of parts and labour at least at a reputable shop.
M/Vorsteiner Aero, P3Cars, HRE R101, Dinan S2, Coils & Intake; Eis/Akra Exhaust
2013 WRX Hatchback:
LED Conversion, Blacked Out, Rally Armor
2015 Macan Turbo:
Techart Exhaust, Cargraphics Lowering Module, Blacked Out