To remove the firing pin on any of the "B" model guns...
Remove the slide.
Using an appropriately sized punch (or a cut-off nail), drive the firing pin retention roll pin through the slide, until it is mostly out of the slide. (You don't have to remove it completely.) A roll-pin punch is ideal, but you can get by without one.
Turn the slide over.
With one hand cover the rear of the slide, and with a finger, depress the firing pin block plunger on the bottom of the slide. The firing pin should shoot out of the rear of the slide.
When doing this, pay attention to how the firing pin is oriented (or look at the parts diagram.) There is a top and bottom, and if reassembled incorrectly, the firing pin block won't engage, and you' won't be able to reassembly the gun.
Reassembly is the reverse of disassembly: put the pin back in and release the firing pin block. This should hold the firing pin inside the firing pin channel in the slide.
Drive the firing pin retention roll pin back in place.