Jeez, that is about my nightmare set of events. I *would not* go a 30s pace in the 500 if you haven’t really done it much before. 5:00 is fairly quick for a high school meet - I’d sorta just try and outpace the guy next to you. If a 5:00 500fr breeze for you, rock on. The issue with HS meets is that there often isn’t a warmdown pool and there are only two heats, so you are gonna get a ton of lactic acid buildup. Do some nice walking around warm down and stay hydrated!