Some thoughts for anyone regarding sensitive government employment.
0. Be discreet. Don't publicly associate your real name with discussions of your present or future work in sensitive areas. If you have/get a clearance, talking about your work in public is a definite no-no. This is also commonly the case in the finance industry.
1. Make sure there is nothing about your life that could be used to blackmail you into revealing State Secrets. If there is, resolve it before applying for a security clearance. Note that being Trans is not necessarily a blackmail-able condition depending on your circumstances, but you will most likely need to disclose it eventually as part of obtaining/maintaining a security clearance. If it is a security concern, they may be able to suggest ways of mitigating the risk so that you qualify for consideration.
2. Don't overdisclose. Answer their questions honestly and completely, but don't answer questions they haven't asked. That just gives you another chance to trip yourself up. Unless they ask about your driving history, they probably don't care about your last speeding ticket.
3. When filling out paperwork, keep in mind that they will attempt to verify the info you provide. If you leave anything out, embellish the truth, or outright lie, they will notice. Be honest. If something about your current life does not match your public records and might flag as a discrepancy, be prepared to explain/clarify. For example, if your driver license shows you with a female gender marker and your birth records still flag you as male, you may need to clarify "Assigned male gender at birth but currently identifying as and living as female." Clarify on the form itself if a place is provided for comments. If you are unclear about how to enter a piece of information, ask.
4. Government agencies can not discriminate based on your GID, presentation, etc. However, that does not mean *every* job opening will lend itself to being filled with a Trans applicant. Be open to multiple job possibilities.
5. If you have any questions about how something may affect your chances of employment or of qualifying for any required security clearance, don't be afraid to ask. The way the government sees it, they would rather have you disclose things *before* they hire you than after. Things you disclose can usually be mitigated somehow. They get really upset when they find out something about you after you are hired that you didn't tell them about; it makes you look untrustworthy. It's better to blow your shot at the job by being honest than to win the position and then end up in prison for obtaining a clearance "under false pretenses".
6. If you have shaky credit or debt problems, get your credit history into the best shape you can; excessive debt may disqualify you from employment and/or clearance.
With all that in mind, best of luck to you if you decide to pursue such a career.