I have one of the best pro-transgender lawyers in Texas, perhaps in the entire US - Phyllis Frye. We've interacted informally at TG Center events over the last year but my first formal legal consultation was yesterday, 9/16. If things go as expected, by September 30th, the last legal vestiges of "him" will no longer exist. Phyllis transitioned herself in the 1970s and now only works a few hours per week, mostly on these sorts of cases or sitting in her judgeship (she's also an elected judge).
I've never heard anything but great things about her and so far, my own experience has been wonderful. I have another legal consultation with her on Monday, 9/22 and we go to court on Monday, 9/29. By the afternoon of 9/29, I expect to have my new temporary driver's license with new name and a nice big F on it for gender and a new social security card. So for me, from start to finish is going to be 13 days. But that's what comes of hiring a professional versus trying to do it yourself.
Changing your name and gender can be done in Texas by yourself but I will caution that the laws here are vague and subject to interpretation widely. The wrong judge will invoke the bible, make fun of you, and deny your request. And he'll get away with that because that is how backwards Texas is on this topic. The right judge will quietly grant your request.
One thing to remember, here in Texas, is to never publicly mention which judge granted you your name and gender change, except when you show your court order for formal legal purposes. No sense giving the anti-trans bigots ammo to run with against judges who do support us, right? Be discrete once you have your judgment in hand.