They are easy to replace. You could look on you tube. Could you post a picture of the broken one?
Basically, you loosen the castle nut on top. The stud which the nit is on is tapered into the spindle. Use a hammer to tap on the area of the spindle in which the taper is set. This is the hardest part. Once you get that separated mark the threads where the end is unscrew the body of the ball joint. Screw in the new one and then place the taper into the spindle. Tighten the castle nut, put in the cotter pin and you are done.