How I Can replace a entire class in the Sims3GameplaySystems ??

It depends on which you want to replace. A lot of them can't be replaced without a core mod. Only the simulator tasks and classes with static/singeton instances can be replaced.

I want to replace the class OccultVampire. It can be replaced?

No unfortunately not. If you want to apply something to vampires when they become one you can listen for the kBeAnOccult event. There's a kLostOccult event for the opposite.