Congrats on trying racing. I did the same this year, and turns out, I really, really like racing. I only have two races under my belt so far, but I have been learning from people with way more experience than me.
(1) You should definitely warm up. My team mates take rollers with them, I take my fluid trainer. Trainer Road has a few warm up workouts that last about 30 minutes, and they work. If anything, I found they gave me structure.
(2) I would not take tools or a saddle bag with me on such a short race. If you have a technical problem, then fixing the problem is not an option, you will typically just hit the time limit and DNF.
To expand on that: don’t go crazy on optimizing your setup. My two races were in the rain, and last time the guy next to me was on carbon rims with 22 mm tires pumped up to who-knows-what-pressure. I was on 28 mm tires at 65 psi and had disc brakes. I felt supremely confident with this setup and overtook tons of people on the downhill. Feeling confident is much more important than losing a few watts in rolling resistance.
Also, I would take one large bottle with me, unless it was extremely hot. And I pack a small bottle with gels, which I would consume prior to the race while waiting for the start.
For each race so far I have tried to set myself specific goals, the first one being to not die (100 % success rate so far!) and then another goal. I race in Japan, so most riders are lighter than me and are likely less powerful in absolute numbers but with comparable or higher W/kg. Hence, I set myself to goal of trying to put the pedal to the metal on the downhill sections to make up for the relative weakness uphill. Oh, and the last goal was to always have a sprint finish.