Should I not let on I can tell he's transsexual?? Advice please!

OK so I don't know if you'd be able to answer this just because you're transsexual but if you are I would really appreciate your thoughts. If you're not  but still have some insight, do feel free to keep reading and comment. So I'm a clueless cisgender person and yesterday I was at this meeting at an LGBT center and this guy walked in late and I could tell he was transsexual, post-op most likely. I found myself really wanting to keep looking at him, because I really haven't been around or even met a lot of transsexuals(that I know of obviously), and I'm not used to seeing a sort-of feminine face with a beard and a male body. I started wondering how much surgery he had to go, like would he have more facial surgery, what did he look like when he lived as a woman, and even "he's good-looking".  Anyway I tried not to stare because I'm sure people do that all the time. Anyway I wondered if he realized I was staring and if he would call me out on it and hate me or something. Then after I went home I envisioned a scenario where he would notice me staring and I wonder if it would hurt him to say "I'm sorry I don't mean to stare, it's just that I haven't met a lot of transsexuals before". Would it hurt him that I noticed he was transsexual?Would it make me sound stupid?  In general, does he just want to be seen as a man not a transsexual man and should I not let on that I notice if the topic comes up?

Please help! I'm such a doof! (I'm going to be seeing this particular guy again)