I did enough research to put together a rough time line and make priorities. I decided to start HRT and begin facial hair removal immediately. I decided that if this led to changes I could not hide before I was ready to be out, I would figure out how to deal with that when it happened. As it played out, circumstances allowed me to go full time earlier than I expected, so this was not an issue.
With regard to voice, that was/is a big issue for me, too. I have done some informal practice and feel fairly confident that I can learn to speak in a way that won't seem dissonant with my appearance, which is my goal. But in the end, I was not willing to wait in the closet while I learned to do that.
From everything I have read, I would strongly encourage you to give voice therapy/training a serious try before planning or scheduling surgery. The surgery changes your pitch, but you will need to learn the other aspects of sounding more conventionally "feminine" separately from that anyway. You may find that you do not need any surgical assistance to change your pitch, and you will not be wasting your time with the therapy in any event.