Some of the factory front sights (at least used to be) pinned on with a plastic rivet. Generally removed by grabbing the sight post with pliers from the top side and breaking it off making it non reusable. The rear is a wedge fit in a dovetail and can easily be drifted out, but reinstalling a new quality replacement I would suggest finding someone with a proper sight pusher. As mentioned above the new front will be secured with a thin hex-head 3/16 machine screw requiring a thin wall nut driver and a dot of blue thread lock.