I didn't let my insurance company know anything other than the fact I changed my name before GRS. Afterwards, when my employer changed my gender in their system, it reported to my insurance companies. The first thing they did was attempt to nullify my marriage by saying my spouse and I were now in a civil union. I challenged this, as did my employer. The insurance company agreed to maintain my spouse's coverage so long as I did not change my birth certificate so that the name and gender on my marriage license matched my BC. Then they went ahead and changed my gender in their system so I could get the proper services for a woman (which screws me up on prostate exams, but I'll take that problem).
The thing is, you want the coverage you need. If you need female services, you need the insurance company to have you as female, or they will not cover you. It sucks, but there's no getting around it.
N.J.