Cold sores?

I have some questions. I had a cold sore about 8 months ago. I had the
first one 10 years ago though. I read about it being possible to infect
someone even if you don't have an open sore.
I'm kind of paranoid about the possibility of spreading it to my
partner's genitals during oral sex. Or even to my own genitals through
intercourse after oral sex. How likey is it? I haven't had any problem
with it genitally in the past. but didn't do much oral sex during that
time either. And I just want to know how likey it is.
Also. having been exposed to the virus during the
past ten years (with no sore during that time). hasn't gotten any cold
sores or other problems. isn't it likey that he is immune to it?
I've had cold sores and shingles but never had chicken pox. Aren't
they all variations of the same virus?