Oh, sweetie, HRT and srs have nothing to do with each other. Even after srs you need HRT. You need to have either E or T in your system to be healthy and after srs you'll generate very little naturally. I'm not planning srs, I doubt I'll ever be able to afford it.
After about 18 months on HRT my libido is like any woman's, different, but present. In fact, as I had low T for decade, it's better than ever.