Whoa, hold on there, Tex! Er, Radar.
The State Department has standardized content for the letter now, and you can find it on this link:
http://www.state.gov/documents/organization/143160.pdfIf you are just updating an existing passport, you don't need to produce a birth certificate because the old passport establishes your identity. However, yes, you will need to provide evidence of your name change, unless you want your old name on the passport!
For the sex marker change, you have two choices. There's a provisional passport that needs renewing every two years--that's for people whose transition is not completed. Then there's the regular ten-year passport for people who are done.
The type you get depends on the wording in the letter. If your doctor is willing to state that you are done--that you have had "appropriate treatment"--then use the letter text that says that. The State Department should then issue you a ten-year passport. Otherwise, you will wind up stating that you are still in transition, which means you have to verify your sex marker every couple of years.
Do not seek out a surgeon, even if you have one. Surgeons cannot write this letter.
Unless they've changed it since a couple of months ago, the letter text that I found (I'm pretty sure it was provided by the State Department) is actually defective. It has a spelling error and a couple of other errors on it. So I tweaked it, printed it out, and gave it to my doctor. One of my doctor's staff retyped the letter, inserting all of his information. I can PM you the letter text, but it's the one for people who are essentially done. Hmm. I wonder if our Wiki has a link to the State Department's letter text? The link I sent you is a bulleted list, not quite what I used.
Well, PM me if you want to see exactly what I used.