"Is it possible?" This is usually a difficult question to answer because anything is possible. However it is not always easy or cost efficient to do so. You have to read between the lines when people answer your questions. If they say 'get the original cab', it's not that they don't want to answer your question. It is just too difficult or expensive to do what you are asking.
In short:
1) NO. Model 2 and Model 3 are different enough that you cannot just swap out components.
2)If you have a Naomi cabinet with one gun game, chances are you probably can swap to another gun game without much trouble. It is possible, but you must read and study the wiring diagrams to check and see. Before you ask, NO. We will not do this for you. You can learn the same way we learn--TRY.