Changing model for NPC/Looking for STALKER NPCs

Does anyone have any idea how to change model for already exciting NPC? For example put snork model on fast zombie or downloading dog NPC from workshop and giving him psydodog model?
Also how to make NPC agressive to player if they priginnaly weren’t suppose to attack him?
Also maybe someone’s know where I can find STALKER mutants NPC?

Hello?(