>>2817732The knowledge of basic maintenance and repair for your vehicle. You're going into the desert in the summer, overheating and breaking down should be a primary concern.
AAA will only tow you from the pavement, they won't go up a NF road to pull you out.
Leave the baseball bat and bring a good shovel.
There is no shame in turning back because a stretch looks sketchy and might break your car. Doing it anyway, breaking your car, and now having to coordinate your rescue while you're in the middle of nowhere WILL make you feel fucking stupid.
A road almanac for the state or offline maps.
Headlamp and carabineers, use headlamp as a light inside the car.
Bring a jumper pack in case your battery dies
A male urinal. Keep it secure in a corner, you DO NOT want to deal with a spilled piss jug in the dead of night.
Window meshes so you can keep the windows open but not invite the bugs in for a feast on you.
Have you done any trips close to home? You might want to start there instead of trying to wing an epic adventure. You'll figure out what you need, want, and are missing closer to home which is much better than figuring that out 100's of miles away.
Check out overlanding (which is just fancy car camping) forums. You'll get some good ideas for what will work without having to go through the pain of figuring it out yourself.
As to "what to see/do?" That's up to what you like to do outside. If you just want views and pictures to prove you did it, scenic vistas are always an easy win and lets you get the legs stretched. Even though I had to cut locations from the travel plans, I have always had a more enjoyable time if I don't rush through because I have to make X miles or locations. Sitting in a car all day starts to wear on you, too. I duct taped a wrist gel pad to the side console for my knee to rest against, highly recommend. Take breaks.
Lastly, don't forget to bring a towel and plan on doing laundry and having a shower. Trust me, just do it.