What is Gender?

With all the stories coming out about "sex-reassignment" surgeries, the evangelical world needs to answer the question "What is gender?," "What are the differences between men and women?" and whether or not there is an indissoluble union between gender and one's anatomy. It seems to me that this is where the challenge against traditional understandings of gender are directed.

For instance:

"What is gender anyway? It is certainly more than the physical details of what's between our legs. History and science suggest that gender is more subtle and more complicated than anatomy" (see whole story here).

And:

"The old categories that everybody's either biologically male or female, that there are two distinct categories and there's no overlap, that's beginning to break down," says Michael Kimmel, a sociology professor at SUNY-Stony Brook. "All of those old categories seem to be more fluid."

Finally, I thought this was a very important paragraph for apologetic purposes:

"So what's different in transgender people? Scientists don't know for certain. Though their hormone levels seem to be the same as non-trans levels, some scientists speculate that their brains react differently to the hormones, just as men's differ from women's. But that could take decades of further research to prove."

If anyone knows of any resources on this issue, I'd really like to be made aware of them. I want to be ready for this because they're coming after us. See for yourself:

"Transgender opponents have often turned to the Bible for support. Deut. 22:5 says: "The woman shall not wear that which pertaineth unto a man, neither shall a man put on a woman's garment: for all that do so are abomination unto the Lord thy God."

Does this verse apply to transsexuals who are no longer the sex they were born? Is sex change the same as homosexuality? Many of the reasons given for sex change that I've read have nothing to do with attraction for the opposite sex, or at least that's not mentioned as a reason, but maybe it is. Is gender set regardless of anatomy? Is there a difference between a person's gender and their sex or are these synonyms?