I'd suggest all of the above -- everything everybody else suggested is something I would have thought of (and do before driving a few hundred miles, let alone thousands).
A $10 90 watt inverter will charge and run your laptop using its AC adapter. Download Google Maps, and if you can, get Microsoft Streets & Trips (one of Microsoft's best acquisitions, and after some years they still haven't ruined it). The only thing better than a laptop with Streets & Trips is a decent GPS, and best is to have both.
I'd change that thermostat - CHEAP way to get some good insurance.
Carry an extra gallon of coolant.
Carry a couple of extra gallons of water, you will use at least SOME of it, maybe more in an emergency.
Emergency belt. That link kind that can limp you to the next stop if you need it.
Flares help on occasion too.
I always carry a spare cap & rotor for long trips. It's paid off before.
Looking to trade for an early 1988 Honda CRX HF (Pillar mounted seat belts)