Chaning gender marker on Certificat of Citizen born Abroad

I wanna know how difficult or if at all possible it is to change the gender marker on a the certificate of citizen born abroad or commonly know as Consular Report of Birth Abroad, "CRBR".

Although I am a full American citizen I was born in England on a joint Air-Force base so I don't have an actual American birth-certificate. I have a "CRBR" and an English birth certificate (go figure) but that's about it.

Has any one ever attempted to or achieved having their CRBR amended. If so was it difficult? how did it work?

 

I'v done some searching on the internet but haven't really found much. So I was hoping someone with experience could tell me. I wanna know what i'm getting myself into.