Change mesh of animation

How do I change the skeletal gun mesh of a reload animation? Is it as easy as just changing a couple things or is it near impossible and will have to be done with an external program like Blended to even make it work?

The gun has a very complex reload with a lot of bones that need to move around, and I’m not sure if I can change the mesh it uses without messing everything up even if it has similar bone names and positions.I’d even be willing to pay someone who’s familiar with the process to do it for me if it’s too complicated.