Since you're in an unusual situation, it may help set your mind at ease if you simply open up with a very short, but earnest chat about setting expectations.
Just something like "hey, I just wanted to get this off my chest, but I'm not really good at stuff like this, and I kinda just want to hang out and see how things go. i don't know how I feel about physical affection, but I know it takes me a long time to warm up to people, and i want to give you a chance but don't want to get your hopes up or anything. that okay with you?"
That last line is pretty key, as it gives the other person an early opt out chance. It's like "click here to accept the terms and conditions" basically. Then once the pressure is off, just hang out and see if you get along.
Kissing isn't hard btw, a single kiss is pretty much impossible to fuck up unless you're massively overthinking it and going a little crazy. A make out session can be judged, but a single kiss doesn't really last long enough to be able to really fuck it up in any even semi-reasonable way. It's sort of like a handshake, even going way, way too hard or soft is just "whatever" since its so brief.