You're probably going to get dropped.
This is not necessarily a bad thing. Lots of people get dropped. At every single level. I got dropped 20 mins into my first race this year despite racing for a dozen plus years. It happens.
Pack skills are absolutely essential. Amazing pack skills can make up for lackadaisical fitness at times. Most beginners have none, though, so a good group ride is vital. What defines a good group ride is up for much debate.
Also, as keeps being mentioned, the surges. The surges are insanity x triplicate. You can try to prepare for the surges on your own, but you likely won't be able to. Once you get a few races under your belt, you'll start to understand, adapt, and improve.
Racing takes a very, very long time to get good at. The vast, vast majority of people that race never get very good at it. Or if they do, they keep moving up categories until they're not very good at it again. It's kinda silly in hindsight.