Hi and welcome.
Sooner is probably better when it comes to coming out, otherwise it just eats away at you anyway. Main thing is to let your wife know that you love her and that is why you feel safe telling her about your gender issues. If she knows that you don't want to leave her, she may be better able to accept things. Nothing happens quickly, and you may eventually find that you are comfortable with one of the many stops along the way. Not all of us end up with SRS or even HRT. We are all different. Hope it goes well.
Karen.