and be warned to look out for events that are happening around any dates you are looking at going... we were out in the Z in that area last year (Cochem and the Mozel valley) and decided to look in and see about going round the ring.... websites said it was open.... called up and they said it was open... drove up there and it was closed due to a rock festival they had there the weekend before... place looked like a bomb had gone off with rubbish and tents all over the place
am driving the Z out to germany again this year but heading further south... Baden Baden and then through the black forest into Switzerland and Zurich
things like fuel costs will depend on if you stick to motorways or go backroads, last year we went france belgium (the ardene area... great roads!) Luxembourg (cheap fuel!) then into germany and then north to the Mozel valley then back via Gent... i guess we did about 1000 miles which worked out at about £250 in fuel.
the eurotunnel is about £100 return and is probably th best and easiest way to go.. been doing ferrys for years before and it seems to take forever compared.
make sure your normal car policy covers you for europe and if you dont already have it get break down cover to cover the same. as for costs on the ring.... i guess they could range from 26 euro for 1 lap to 20,000 euro plus for 1 bad lap ending up in a barrier with a closed track! i have heard horror stories of bikers still laying on the floor and being given tickets for the damage their bike has caused!
if your going to do a few laps dont try and be a hero... take it easy and enjoy it but factor in a tank of fuel and make sure you have a good set of brake pads and tyres in place before you start or you may end up having to factor in the cost of replacing them in germany (depending on how many laps you do!)
i do plan to do it at some point although i hear they are making it harder and harder to do the tourist days???