You don't have to take off your calipers. You don't have to take anything off except to unbolt the fender and the speedo cable from the fender.
That said, it WILL NOT just slide right out....it's close, but not quite....however, it will come out simply by holding boths sides of the fender and squeezing the fender enough to clear the forks.
After you install your fender extension, squeeze it together again to go back in between the fork tubes.
You can also help to protect the fender by slathering a bunch of blue painters tape all over the sides of it prior to removing it past the fork tubes.
The above method worked great for me.

