What are you most worried about?
When I did my first challenge (Princess’23) - which was also my first ever race event- I prioritized sleeping well (I changed my usual wake up time one week in advance); resting and recovering (stayed at the hotel, by the pool, reading, etc after each race); eating well (no “new” food or anything new for nutrition/hydration on the races)…
I have participated to all challenges ever since

… and now I go to the parks on the expo and 5k days, might even go on the 10k but still try to sleep better before the HM… going to the parks with the medals is super fun… there was one weekend though that I overdo myself in the parks and ended up with shin splints on the Half… so I guess is trial and error…