Hi Andrew,

it should be about 500 - 600 km (350 to 400 mls.) from Munich to the Ring.

According to the timetable it is only opened on the 24th of October - be careful on that day since usually a lot of people will be there on Sunday.

The Ring is officially a toll-road when driven on the tourist days so driving with a rental car shouldn't be a problem actually. I'd be careful with this comment since you can easily lose your insuranse when they can prove you a serious misuse of the car (e.g. passing on the left and driving on the ride side of the track is officially mandatory, speed limits are effective on the Döttinger Höhe at the tourist gate and at Breitscheid, the 2nd exit on the track).

Be careful when you drive in the wet, the road surfaces and conditions can vary every couple of kms - be very careful! Take it easy in the first lap, especially in the corners.

Shouldn't you be able to make it to Nürburg, try the Hockenheimring. They also offer Tourist drives (they are opened on 28th of October from 17:30 to 20:00 in the evening). 15 min. for 12 Euros, which is about the same price as one lap on the Nürburgring!

Feel free to ask or PM if you have any further questions!

Greetings!