What I need for a trip into mainland Europe

[Yorkshire Lad]

Planning a week touring Germany in June, Porsche factory and museum, Auto Salon Singen, Motorworld, Deutsche Alpenstrasse, BMW factory and finally to the Nurburgring for some spectating.
I have read somewhere about an emissions pass to enter some of the cities. With us going into Stuttgart and Munich, is this something I will need to get and, if so, where do I buy these.

Also, are there any more "must haves" or "must do's" that I need.

All advice will be gratefully received.

[Yorkshire Lad]

Thanks for all the information gents; I'll check out the AA website.