This is great to hear, I've signed up for the Art Bourne Memorial at the end of the month, it'll be my first match....have to admit I'm getting a little nervous having never shot in an official match of any kind.
Well, as Cyanide said, if you can show up on Friday (ask when the gate will be open), once all the targets/frames are set up and wind flags are planted, there's usually a sight-in period: a few volunteer to mark targets while others sight in, then swap over while the first bunch marks targets. By the way, this teaches you how the shots are scored, and gives you some appreciation for the job the target markers do on the day of the match. Often the wind gets blowing hard there, and sometimes the markers are having to hold the target frames steady in the wind. And you'll definitely learn about correcting for the wind, too

In the matches I've attended, they start at 300 meters, so once you're sighted in at that distance, you'll be good to go on the day of the match. Moving up to 500 meters is merely an adjustment on the scope: mine is somewhere around 20 clicks upward if memory serves.
On the day of the match, it usually goes like this: they'll post the relays (who shoots, in what order, and on which target) and let's say you're assigned to target 4. Find out who shoots immediately before you on that target, so you'll know who you're following. When that person finishes their string, they'll pack up their gear and then move to the small seat/desk behind the shooting ramp (the slightly inclined, carpeted surface you lay down on to shoot), where they will score for you when you shoot your string. When you put your gear and rifle down on that ramp, hand the previous shooter (now your scorer) your score sheet. Each shot you send downrange is marked by the target pullers, and the scorer behind you will mark those values down on your score sheet until you're finished. Once you're done your string, remove your gear to make room for the next shooter, sign the score sheet your scorer will have ready for you and hand it in to the person collecting them, and get settled in to score for the next shooter. There'll be a spotting scope for you to watch through.
Don't worry, you'll be taught how to read the markers on the targets so you'll know what the scores are, and it will all make sense as you go along. It is confusing at first, but you'll be fine. A couple of points: at first, it's startling to be concentrating on your shot and then have the guy next to you take his shot, or the shooter on each side of you let go almost simultaneously, and this can startle you into pulling your trigger before you're ready, but you quickly get used to that. The other thing that I had to do when scoring is keep myself concentrated on the shooter and his/her shots, and which shot it is, and the score, and not get distracted by the other things going on around me. It's embarrassing to have ask the shooter "Um, was that your fifth, or sixth shot?" Ask me how I know...

Oh, and when you're shooting, as obvious as this sounds, do make sure you're shooting at
your target, and not the next one over. Crossfires do happen, but they're embarrassing too!
One last thing that's very cool to see: when you're scoring for the shooter who follows you, and you're watching their target through the spotting scope, you'll notice that as they take their shot, you can actually see the wake of the bullet as it goes downrange and hits the target.. You can soon almost begin to tell what the score will be, based on what you're seeing.
When I compete, I'm really just competing against myself. I know there are many more experienced shooters than I, and I will likely not be winning any gongs, but that's ok. I'm there to learn, and have fun doing so. You'll learn a lot, and some of the scores you'll see are amazing. A great facility, and a great bunch of folks, too. Best of luck, and enjoy!