i didnt replace them... but its not hard, ive done it numerous times, it just takes patience. my car has 5 layers of paint on it, so i decided it would be best to go off a clean slate, so i stripped it down to the metal and started from there. the fenders are being replaced ( i have them they are just not going on untill i paint the car ), and everything else that is green is getting scotched down and sprayed becuase they paint is in great condition there.
In response to replacing them. Its expensive because it is time consuming. to do it you basically have to section out your quarted and section in a new one. IOt takes a bit of shaping, welding, filling etc to make it perfect.