It is just about as simple as pressing the old ones out and pressing new ones in, however there's a little more to it than that.
You will obviously need to remove everything from the knuckle then loosen the castle nut on the top ball joint. It's going to take some force to get the knuckle off the inner C. I had good luck swinging a dead blow hammer on mine, however there's got to be another way.
With the knuckle off the vehicle, a press or balljoint service tool will make quick work of removing the ball joints. I recommend using a hydraulic press. You then press the new ones in, paying attention to which way the grease zerk fitting is pointing (making sure you can get to it when its on the vehicle), and set the knuckle back onto the inner C. Somewhere on this site you'll find the torque specs for the nuts that hold the knuckle onto the inner Cs, and you'll then need to set the preload on the top castle nut, that data can also be found on this site, just use the search function.
At this point I would recommend getting your alignment checked. It is also a good time to consider camber correction either in the form of spindle shims or the caster adjusters available from BC Broncos. I was surprised how far off my alignment was, and how much better my truck drove once all was back together and aligned.
