I would echo the recommendations to not try drive the ring after a commute from Munich. You want to be as fresh as possible. Remember, on the autobahns, if you're going at speed, you'll get fatigued from concentrating….though you won't be sitting on 100mph all day, there lots of speed changes and the odd 'stau' to slow you down...
You can stay right near the ring in Adenau - there are a few decent hotels that cater to 'ring visitors. We stayed here, and it was quite good:
http://www.blaueecke.de/
If you can make time to go through Stuttgart, you really shouldn't miss the Merc and Porsche museums. The Porsche museum is amazing! (I'd say better than BMW and Merc…though Merc has some awesome history and the building itself is quite impressive)
You'll also want some spare time at the Ring to visit Ring Werk and tour the F1 track etc...
Here's some other people's experiences at the ring:
http://www.ausringers.com/your-story
http://www.ausringers.com/links
and a useful ring planning site:
http://www.nurburgring.org.uk/
Make sure you look up when the tourist days are running at the 'ring. It would be a shame to arrive and find out the ring is shut while you're there….
http://nurburgring.org.uk/calendar.php
http://www.nuerburgring.de/en/angebo...dschleife.html
Finally, you can't drink beer in Munich without at least trying the infamous
hofbrauhaus...
edit: also - might be worth familiarising yourself with German road-rules....especially for the autobahns...could save you some heartache...