Replace Mesh in Realtime

I am working on a fps with only the arms showing and i want it so if an axe for instance collides with the arm it replaces the arms mesh with half an arm which it term gives the illusion of the arm being cut in half. also to make the front half dynamic so it falls onto the ground, which i have another mesh for that. And change the texture of the arm so it appears covered in blood

you can actually split the mesh modifying the mesh with the mesh class or else you can have 3 objects

A whole arm and 2 presplit pieces made in your modeling tool.

you simply spawn the 2 halves directly over the whole then destroy the whole.

Thanks Sparkzbarca! but how would i script this to appear in the same spot? even if the arms are animated?