Hylton... the front "pin" is not a pin at all. It is as others have told you, a spring loaded button.
The trigger guard of the AR-15/M16 is designed to be operated with that universal M16 tool that every grunt has, a 5.56 bullet tip. If you don't have one of those, you don't need to fix your rifle. That tool was used for adjusting sights, too, on the old A1.
Anyway, the trigger guard is made to swing down, after pushing in the front BUTTON with a bullet tip, so that the trigger may be manipulated in cold weather, with thick glove or mitten.
If you will look at the rear pin, the trigger guard is held on each side by a thin aluminum tab, about 1mm thick. If you were to hammer with a punch on one end of the pin, it would put pressure on the opposite tab and break it off. This WILL happen if you don't support that other tab.
(BTW, toss out that PLASTIC trigger guard
and buy a real one made from aluminum.)
When you reinstall the pin and new trigger guard, here is one method...
The ViseGrip's jaws are taped with electrical tape to prevent scratching. The handles are adjusted so that with each squeeze, the handles just barely close, moving the pin only about 1/16" with each squeeze. This puts the handles in the position that gives the most mechanical advantage and most control. A little grease in the hole helps, too.
Then just tap home the final bit with the hammer and a punch or nail set, supporting the other side on a hard surface, such as the "anvil" surface of a bench vise.