Im sure the undersheilds need to be also M5, whcih means new mounting brackets. I dont know what year 5 you have but if the foglings are square, M5's are more oval, then you have to take into consideration of paint, bumper mounting points and if your 5 doesnt have the back door trim all the way around it wouldnt the back trim on the bumper look a little werid? Tell her your pay for an oil change or some service, much easyer for you.