kris,
I've done it both ways. Some songs I change to fit my gender, some I don't. It depends on the song, and how I feel.

Some songs don't work well changed (very few men on a farm wash clothes while their wife is out behind the horse with a plow, at least not in 1870) On the other hand some songs aren't gender specific except for a few "him"'s, "He's my true love" and such things which can be easily changed in which case I will.

Personally I enjoy challenging myself and everyone else by changing it. Although it comes as surprise to to those who know the song, I think the change is good, it gets you to really pay attention to the song again. The song actually becomes fresher when you hear it done a little wrong. So don't be afraid to change it. Besides, this is folk music here, it will change over time and you need to do your part!

For the few songs that don't work as the other gender, that is why I call myself Rachel. :) Just pick a name, pick an identity, and run with it. It is much easier for me to sing about holding a baby while washing clothes while my husband is out plowing if I can imagine myself in those shoes. Sometimes I even change the words to fit. (my husband doesn't come in and say honey, it is "my beautiful Rachel" which no real man would say, but which women either want to hear, or hear in their mind. All of course depending on how it fits.