This information was accurate up to December 2000. If you find any of it is outdated please let me know so I can update it.
DMV:
You need to fill out and have a DOCTOR (read MD) sign a DMV Form DL328. One the the gals from my counseling group had our counselor sign it (a PhD, but not MD) and had to fight with the DMV before they reluctantly (they didn't have to) took it. I had my endocrinologist sign mine and it went through without a hitch. Make sure you make copies after it is signed. I was told by my endocrinologist to not date it (the DMV bases the amount of time your new license is valid on the date) so you should date it right before you give it to the clerk. You also need the Driver's License/ID Card Application form DL44. You must get this from the DMV because each one has a unique serial number & barcode on it.
Make an appointment (licensing deparment) to save time. Give your feminine name (they don't care) so you don't get outed when they call you to the window. The clerk will take the two forms (DL44 and DL328) and your current Driver's License and/or ID Cards. You must surrender them so have them with you (I begged to no avail for them to punch it and let me keep mine). Next, the clerk will have to call over a supervisor to get an authorization and may ask for help if they've never done this before. (Note: They will offer you a new Driver's License number. Don't take it unless you have a major reason why. I've been told your record is sealed after the form is finalized anyway so people can't find out your prior name. Only citation information will be visible to them.) Lastly, they have to look up the authorization code in their manual before they can enter the change. I got the chapter/page from Sacramento so that saved time because I was able to give it to them (They don't do many of these). I is Chapter 4 pg 46. You will also need to change your auto registration separately. Fill out a Statements of Fact Form REG256, Section H.- Name Statement.
Something else you should be aware of. When the DMV takes your current Driver's License and/or ID Cards they only give you a reciept with no picture. Be prepared to go without a picture ID for up to six weeks! If you fill out the voter regestration form attached to the back of the DL form you will get a receipt with you old and new names on it on DMV stationary. This will be the only official document you get that shows the change. Very handy for those cases where you must prove who you WERE.
SSA:
You should be prepared to go to a Social Security office soon after. The DMV now matches names via your SSN and if they don't match will cancel the transaction. You will need a Social Security Application Form SS-5. The clerk here will need a copy of something with your old name and something with your new showing the change. Use the voter registration reciept (or an old library card, etc.) and your temporary Driver's License. They will NOT change your gender. You must change your Birth Certificate (after surgery) for this to be changed. I've been told you get higher benefits at retirement if you leave it male anyway and NO ONE can see it. Social Security records are the hardest thing to get at, even with a court order.
EVERYTHING ELSE:
Use the receipt from Social Security and temporary Driver's License to change everything else. For a few things you may need the Voter Registration reciept (Bank will probably want it) and/or a copy of the signed DL328. I had to send the FCC the works to get my ham radio license changed. I also used a Declaration of Legal Name Change which I found in the NOLO Press book "How to change your name in California". This looks official enough to satisify those who want to see a legal document (which isn't necessary).
Note: (An attorney may disagee with this. Please e-mail me if you know more.)
The way I understand things- You will be the new gender for just about everything. Everything that doesn't rely on your Birth Certificate. You will still be your former gender for Marriage, Medical Insurance, certain legal reasons (read incarceration) and on most Federal items such as Passports.
One last form that may be of use National Voter Registration Form.