I actually had a similar conversation with my partner not too long ago. If my Dad walked up to me and said he wanted to transistion, it would take some time to switch titles and pronouns, just like it will take him time to do the same for me. I don't really know how I would take it, but I like to think I would be supportive. My father has done so much for me and sacrificed so much for me and his other kids. I want him to be happy. I told him the same thing when he married his current wife, whom I don't like or get along with at all. But, it makes him happy, so who am I to throw a fit over it? I like to think I would offer him the same support that he has offered me throughout my life.