Model swapping is a more complex process than what we've seen so far. It definitely will require you to have knowledge of 3D modelling. Even though you won't need to model anything, you will have to process the models you want to get into the game. I work with 3Ds Max. There might be ways to do what I'm going to teach you in other programs, like Blender, but I only know how to use 3Ds Max, so I won't be able to help you with that.