Agoodbygirl raises an interesting point. I have come across many frum men and women who worked in tyhe non Jewish world without compromising their Yiddishkeit. Be sure to set an example, a kiddush Hashem at all times.
Using first names is the norm out there in the world, and although not our way is not a halachic problem. Avoid any socializing with them outside of the office which I’ve found is understood by co workers. By your dress and use of language you will stand apart anyway.