Hey there! First off welcome to the community and have fun!! Been there 4 times and it's a unique experience compared to other NASCAR races. Lets start with...
Equipment I strongly suggest you bring some real cold beverages, like /u/Walkingtalkinghawking suggested. Mainly, water. Have a cooler full of beer, but a backpack, maybe of water. Speaking of backpacks, you may want to pack some full of lunch and other goodies, as the food is expensive(but DAMN it's good).Where a hat and shades, and one of those funny seat cushion things, as the stands, except the main, are stone. Sunscreen is a good idea, it's one of the only times I wear sunscreen in the year. Bring a blanket, cause there are some spots of grass you can lay down on. Earplugs are not necessary here, as the cars aren't on wide open throttle all the time, so they aren't as loud. That's about it, things you would bring to a typical race.
Seating Sitting in the stands will roast you, as is one of the most infamous things about going to Sonoma. Speaking of sitting, the main Grandstand is plastic, and the upper parts are shaded by the roof. Sitting anywhere else, however, the seats are made of stone, so bring a cushion of some sort(no folding chairs allowed in seating areas). But, it's Sonoma Raceway, and the facility is huge! Me and my dad never sit in one spot. You can walk all around, and the tunnels that bring you from one side to the other. Walking around gets hot, so ware a hat and shades. It is beneficial though, as you get to see different areas of the racetrack, the racing is different is certain spots, and the cars sound different (I was sitting at the straight right after the S's, heading into the hairpin turn last year, and they make a wicked high pitched screech as they brake hard heading into that turn leading to the hairpin). But, don't plan on sitting in any designated seating areas. The mean event staff will ask for tickets, and if it does not match the exact spot your supposed to be in, you shall not pass. Find a fence to lean on, or, like me and my dad, get lucky and sit under the shade produced by this snow cone trailer.
Sights to see I mainly focus on the race, if you can do that for a billion hours. Nevertheless, there is the famous ferris wheel. No idea how long the lines are, but seeing the amount of kids every year, it shouldn't come to a surprise. Behind and under the main grandstands, there is a alley of concession stands and gift stands. They are spread out everywhere, but then again, I don't suggest buying food there. They're all actually insanely good and well loaded food, but a backpack with snacks, or even subway/safeway sandwhich's or whatever you want. Just bring a backpack with a few lunches and snacks packed away(and drinks). You can also stroll around the... I have no idea what it's called, but the area behind the main stand, that also serves as the hauler parking and garages, that has a lot of promotions from sponsors, simulators, games. I honestly don't know what is all there since I'm usually on the other side of the track, but, its the area with a lot of tents!I'm sorry I don't know how to better explain it. Better advice, just adventure around. Seriously, the place is huge, and there is much to see, I just can't remember the names of specific places at the moment.
Transportation and Getting in and out of there First off. I reeeeaaaalllly hope you guys have a good, stable, reliable, serviced, trusty vehicle to get you there. The tempature, is, like I said, an infamous part of Sonoma, on some days. I've seen brand new, high end cars puke their coolant out just when idling. And depending on which gate your entering, your car may need different needs. Gate 9 is a very scenic, fun drive to the tracks, but it's up a damn hill, with a dirt path. A powerful vehicle with decent suspension is recommended. If you got the cheap tickets from a Savemart or Lucky's, you will be heading to Gate 7. It's all uphill, and it's usually traffic going up that hill. That means good brakes, a vehicle that doesn't roll down an incline that easy. If you do, you'll end up with your bumper, inside someones radiator. Keep your distance as well. If you're heading to the main gate, good luck on Sunday, but if you are staying at a campground for all 3 days, YOU ARE SO LUCKY BECAUSE I'VE ALWAYS WANTED TO CAMP AT SONOMA RACEWAY. But if you plan to leave and come back, then on Race Day (pssst, thats Sunday, Sunday, Sunday!), if you are coming from Highway 37, holy shit, I wish you all good luck. It's bad enough every day, but combine it with commuters and NASCAR fans, and it gets ugly. LEAVE EARLY...REALLY DAMN EARLY, or camp there. It looks like great fun. Leaving the track, is, as you can expect, some fun. There will be traffic, obviously, but I found it fine cause when leaving, I got to stare at the beautiful hills we parked on top off, and the sheep. That's right, Sonoma Raceway has some sheep.
Extra Notes The NASCAR weekend at Sonoma is an incredibly unique experience. There are a lot of events going on, and the scenery is stunning. Let me know which way you are coming to the track from, and where you are sitting, but like I said, don't just be chained to one spot, move around and adventure. I'm not going to tell you places to see, I want you to get lost and explore all Sonoma has to offer. Because trust me, it has a lot to offer.