There are several places in Germany that can answer that question. Start with a military base (Kaserne) transportation office. They know the requirements. The answers are free. You probably won't like the end result..... about 3-5K for the conversion.
Warning..... when you return to the states, maintenance will be much different for you because your car will be considered a "gray" market vehicle. There are subtle differences in things like oil filters, light bulb replacements, ect..... Many of us weighed the additional costs and just decided to bring back an american spec vehicle instead. In the long run, you will dish out more $$$s with a euro spec vehicle...
Been there, done that.....
Good luck!!!!