You're talking the seal above the pitman arm? yes I have pulled those out in frame but it is very trickey.
But first be absolutely sure it is that seal that is in fact leaking, and not something higher up, like the two little o-rings under the control valve housing, which is much more common.
After the arm is off, you will be able to see the seal. Check to see if it is pushed up far enough to see smooth shiny output shaft.