First off, the firing pin for those guns is made in two pieces, since a one-piece pin can't be put into the slide. Removal is pretty easy. Using copper or leather jaws, clamp the slide firmly in a vise, making sure not to "pinch" it at the bottom. Now using the proper size punch, preferably a hollow end type, drive the firing pin lock pin out left to right. Make sure to catch the firing pin parts and the spring. Install the spring, then the front firing pin, then the rear. Use a smaller punch to get the cut in the rear pin aligned for inserting the firing pin lock pin. You may want to use a work* pin, slightly smaller in diameter than the lock pin, to get things lined up. The work pin is then driven out as the lock pin is driven in.
*We used to call them "slave pins" but that word is now a no-no, not PC.
Jim