There are four conjugations of pronouns in english - subject conjugation (he/she/they), object conjugation (him/her/them), possessive conjugation (his/hers/theirs), and reflexive conjugation (himself/herself/themselves). If you replace all instances of him with her, of he with she, and of his with hers, you will still have a fully grammatical english sentence. It is exactly that simple.I would implement it by calling the 4 functions:
I am also 100% sure I could code this option to default to "he/him/his", so that no one would notice if they didn't go looking for the option.
((Also: if you really want to know how helpful adding pronoun options would be to the women using your program, you could always, you know. Ask the one you're talking to.))
GetHe(), GetHis(), GetHim(), GetHimself() wherever I used He, His, Him, Himself, respectively, but even then it's more complicated than that. For example, I'd also have to pass if it's capitalized or not.
Also, I'd have to break up the string generation code I have, which will not only take time, but it will introduce more possibility of bugs, and the additional complexity would make debugging other things more difficult in the future.
And as I said before, it is perfectly acceptable grammatically to use "his" as gender neutral in situations like this.