I'm going to ask my friend to leave his wife out of some stuff
Why do you not want him to leave her out of things?
Because he is always telling her stuff and I need him to give me extra help with something that I want to keep private?
If there is something you want your friend to keep private from his wife, you should not tell him anything. He has an obligation to share things with his wife.
I'm going to make him get rid of her
Trying to make him get rid of her will not address your issue. Simply keep your private matters to yourself so that you do not put him in an awkward position.