have 686 that iam replacing firing pin to an apex xp ,due to light strikes , do i have to take hammer all the way out? or can i just cock it, to let the old firing pin slid out ,once i pull the retaining pin put?

You can but I wouldn't. It stresses the frame studs because the sideplate (half of their support) is gone. Back the strain screw way off and lift out the hammer. Plenty easy to do.

thank you tom cat 51