It's not just when you go. Provision for when you get back.
As a minimum i would go with, new, known tyres that i have some confidence in. The Ring is that large you can get between 2-3 corners and have blazing sun to rain, so get a good allround tyre that YOU know are good. Provision to be replaced when you return.
At a minimum for brakes i would disks, new fluid, performance pads and uprated hoses - provision for the discs and pads to be replaced when you return.
Geo check, check your tracking, camber, caster to ensure you have a straight car.
Breakdown insurance. Cash for laps, a go pro, ears to listen to the locals and for other users.