About fat embolism. During surgery it is normal for very small amounts of fat particles to travel through the blood stream. It's not something that either does not happen at all or completely escalates. It's more of a certain percentage of fat particles that will always enter the blood stream with very low likelihood to cause serious problems or fat embolism, this is why it's also called "embolism complication". Embolism itself, a substance entering the blood stream, does not always cause problems.
Since this is a percentage based success-outcome, you need a good doctor, or at least not a bad doctor.
Other than that, I would guess not being fat helps too.
I would tell my (potential) partner casually along the way about the surgery, before the relationship is official. Basically, you want to make sure that she knows your personality enough, to overlook it, because it will be not an issue, if nothing is wrong with your personality. I would not make it a topic during the first encounter is what I'm saying, because that would also imply how much of a deal it is for you to mention it at the first opportunity. Just treat it as something you did many years ago, with that kinda mindset as if it has always been part of your long past.