Miss Manners may have taught you how to deal with males and females at work, but she never told you how to deal with transgendered individuals who have either changed genders or is in the process. The good news is that transgender etiquette in the workplace is similar to the good manners and etiquette you already know.
He or She
Learning to address someone by a new name and gender-specific pronoun takes some getting used to, but you should respect the person's decision. If Bob is now Barbara, address her as your would any other female in the office. If you make a mistake and accidentally call her "Bob," avoid making a big deal over it. Just move on and try to do better next time. For all purposes, Barbara is now a woman.
You may have a lot of questions about the transgender lifestyle and the medical procedures required to change sexes. But, limit your questions to work-related topics unless you have a friendship with Barbara and she has opened the door to personal questions. Most transgendered people are more interested in leading a normal life than being a spokesperson for transgender education.
Gender vs. Sexuality
Do not confuse gender for sexual preference or assume a transgendered person has kinky sex or low morals. Barbara may have felt like a stranger trapped in a man's body, but that does not mean she was ever homosexual or dates men or is married to a woman. Her gender preference has nothing to do with her morals or her kink level anymore than any other women in your office. Judge her by her actions at work and give her the space to be the person she is.
Above all, respect the transgendered person for having the courage to make a most difficult decision and be supportive. Avoid outing Barbara to anyone who does not know that she used to be Bob, and strive to treat her as you would anyone else in the company. With time, you will forget all about Bob as you grow to respect and appreciate Barbara as a qualified, likable part of the team.