The second hardest thing about a new Mustang is breaking it in. However I will start off by saying the break in procedure can be argued just like what is better automatic or manual, Fastback or Convertible, 1/4 mile or the track and so on and so on. Myself I drove mine easy for the first 1000 miles and changed the oil and filter at the point and then found out just how fast it is. So if you choose to "break her in", it can be hard at times. A friend wants a ride in your new Mustang so what are you going to do? Like I say the break in can be the second hardest thing that you do with you new Mustang.
fd