I spent 4 years in German while in the military. Unless things have changed, military DO have to pass a written drivers test. The test will really test your memory skills too. Besides several text questions there's approximately 150 signs to memorize if I remember correctly. Took me two tries to pass the test.
How far from the Autobahn? Not far. Every major city is connected with Autobahns.
Hell, you can drive across the country in approxiately 8 hours (north to south).
Here's a few driving tips:
* Even though there's no speed limits on the Autobahn's, there are a few posted speed limits on some "sections" of the Autobahn; nearing Frankfurt for instance. Better obey them too.
* Typically 50km/hr between small towns, and police are dead serious about that.
* NEVER get in the left lane on an Autobahn unless you're passing.
* If there's a posted sign -> don't ignore it. Germans love their autobahn's and race like mad-men from point A to B, but most are absolutely serious about following laws. Even parking signs.
* Never test the patience of German police, you'll lose in a big way.
* If you come upon an accident on the autobahn and traffic comes to a stop, do what the rest do. Pull off the road. Emergency vehicles will be coming up the center - fast, and believe me, you don't want to be in their way. (Pisses the police off.)
* Don't expect the Autobahn's to be the quality of a race-track. They aren't. While some have big sweeping turns and are nice to ride fast on, others have deep ruts in them which collect rain water nicely or have poor overall quality. Once you get out into the country Autobahn's may only be two lanes in each direction, and you'll be saying to yourself, "This is an Autobahn?!"
* NEVER think you're the fastest thing on the road. Trust me, you'll be handed your hat in short order. Germans are used to driving fast. It's one of their pastimes. Your Busa @ 150mph will keep up with most of the stuff, but not all. I owned a 1969 SS396 Chevelle when I was over there. I thought it pretty fast. Wrong! I was typically embarrassed as micro-sized Fiat would blow past me while I was humming along at 125-130mph, (not to mention being occasionally passed by the REALLY fast stuff going 160-190+mph).
Good luck over there. It's an interesting place.