In M2F surgery the penis is basically skinned (flesh removed), turned inside out and positioned into the body cavity to form a vagina. It's done in such a way as to leave all nerve endings intact so sensation is felt and orgasms can occur. The scrotum is used to construct the vulva (labia majora and minora)
F2M surgery is much more difficult. Some F2M's use only HRT to enlarge the clitoris, which forms a small penis, capable of penetration. Others will have a penis formed using skin/tissue grafts from another part of the body to form a penis.
Both fascinating surgeries.
Those who have undergo either surgery have spent years struggling with the decision and undergoing extensive mental evaluations (not to mention the possible loss of family, friends and jobs). Their plight is not one to be made fun of but one we should strive to try and understand. Nature is not perfect and it too makes mistakes, all they are doing is trying to correct that mistake and live a life they can hopefully find personal peace and happiness with.
To answer the OP... I wouldn't care. It would be their decision whether they wanted to tell me or not. As with all my sex partners, if I find something I like and/or am attracted to, it's game on.
Teresa