I was nervous too, but it was a piece of cake, truly. I had mine about a month before surgery, and was probably as nervous about the cath procedure as I was about the surgery itself. But it turned out that was silly. The cath procedure is safe, painless and quick. Your arteries have no feeling, so you don't feel a thing. It's an outpatient type thing - go home later the same day, although they keep you there for observation for a few hrs first. I easily could have gone back to work the next day, but took it off just as a precaution.
As far as the procedure itself (and please remember I'm only speaking from personal experience - they may do this slightly differently in other hospitals) here's what I remember. They wheeled me into the operating room while I was wide awake - which was a little freaky, but not horrible. I remember getting up onto the table (pretty much by myself if I remember right). They sedate you pretty heavily, but don't knock you out completely. So I remember them putting the IV in, and then it gets fuzzy after that, lol. I remember telling them - don't be afraid to crank that sucker up - in fact, I'd rather be asleep. But there was some reason they didn't want me to be totally asleep, so I was just kind of semi in la-la land. I remember parts, but not all of the procedure. I think I got some local anesthetic down there where they were working (in the crease at the top of my leg, but more toward the top as you're laying on the bed, not down between your legs like I was afraid it might be). But I was getting pretty fuzzy by then, so barely remember the local. I vaguely remember them working down around my groin area, and them telling me they were putting in two lines - one in a vein and one in an artery. I think they told me there could be a warm feeling rush over me as they put the die in, and I vaguely remember feeling that. I vaguely remember being a little worried about my heart skipping a beat or two while they had the cath in there, because they'd warned me that could happen. I don't remember if that happened or not though, lol. I couldn't even really tell when they had the cath up that high and when they didn't. Didn't feel a thing. Must have dozed off for a few min, cause next thing I remember is my cardiologist waking me up and telling me the results. In my case, the results were - yes, it's time for the valve to be replaced, but no, you don't have clogged arteries (those were the two things they were checking for). Hope that helps a little. Honestly - don't be scared about this one - it's easy peasy!!!