Hi Knave,
Just to answer some of your questions...
What eljockvis said about the prices is very true, and only looks to increase as time goes on....
I personally drive from UK to Germany (where the in laws live) to get my car serviced, there are 3 big BMW garages in a 5 mile radius, 1 with an M technician. The price difference actually pays for the trip and IMO the work carried out and the service you get is much better.
As for the measurements U.K. does distance in miles...the rest of EU does the in Kilometres so you should be okay there. 1 gallon UK = 1.2009 gallon US so 1 US gallon = 3.785 litres. so for a rough price 1.08 * 3.785 * 2 = $8.18 per us gal. (damn that tax man

)
As for insurance, which is compulsory, it can vary completely, it goes on age, time held licence, any convictions (speeding etc) type of car, years no claims, location and predicted annual mileage.
Try getting a quote.. I have found admiral.co.uk to be the best for me personally but there are 100's of company's out there.
HTH
As for the autobahn...... I would hurry, at the moment the German chancellor, Angela Merkal (excuse spelling) is putting a stop to the 'greenie's out there' wanting to put an 80mph limit on the autobahn network, but when she goes it looks like the only unrestricted roads in the world will go with her! As this months EVO mag says, the traffic for the nordschleife will stretch to Calais...