Leah, while my wife is still reluctant at times, and doesn't like to touch the subject, she has told me already that she will stay with me to the end. Not sure where that end ends

but I will move forward and have a chance to stay with her. So, it is possible to stay married if that is what both of you wish and if you love each other.
In my case, I just spit it out after some bottles of beer. I think it was better this way, even with the impact it had. It is tough, no matter how you tell. If I made up a speech or rehearsal for telling her, I may have chickened out

But one thing you have to do... let it out. The more you hold it within you, the quicker you get depressed and what more... don't let that happen.
And of course - a therapist will help you deal with this moment and give you the tools you need for outing and further proceed with the transition if you want. If not, someone neutral that you can speak and will understand your concerns (of course, if specialized in gender/sexuality, make sure it is).
Good luck and keep us posted!