Dear Angie,
I second the gender therapist recommendation. Who knows, you may discover that you do not need to transition, which may give you and your wife comfort. If you determine, through counseling, that transition is necessary, your therapist can help arm you with the knowledge you will need. And, perhaps, you and your therapist may get your wife to accept it as well. Of course, if you do need to transition, your marriage may not last. Not a lot of women signed up for marrying another woman, unbeknownst to them at the outset.
Good luck and keep your chin up!
Cate