Since some are talking about two different things (Int Drivers License v. German drivers license), lets be very specific here.
To get an International Drivers License, you do not trade in your USAREUR license. Instead, you simply need a form from the USAREUR drivers license office and one or two passport photos (form will say how many). The form will also tell you where to take or send it. If not, as another said, ask the drivers license office.
You cannot use your USAREUR drivers license to obtain a German (EU) drivers license
. However, you can trade in a stateside drivers license
for a German (EU) drivers license (no test, no school) if that license is from any one of the many states with a reciprocity agreement
with Germany. Moreover, when you return to the USA, your state will also accept that German drivers license in place of the practical and written tests when getting another license there.
You can find out more about that at the American Chamber of Commerce Germany website here: http://www.amcham.de/services/drivers-license/us-citizens-in-germany.html
We (wife & myself) have both now traded in our stateside drivers licenses twice for German drivers licenses (pre-EU and EU). In both instances, the process was quick and easy (under 15 minutes). You'll need a residency registration certificate, a certified translation of the stateside driver's license (ADAC or USAREUR drivers license office), and a passport photo. The AmCham website will explain.
The German drivers license office will take your USA license, send it back to the issuing state, and give you a temp drivers license for Germany. The actual license will arrive in the mail in about three weeks. Most German drivers license offices have translators to deal with the many foreigners obtaining licenses, so language is seldom a problem.
When we returned to the states previously, Washington state accepted the German drivers license just like a license from any another state. We simply filled out a form, gave them the German license, took the eye test, and walked out with a Washington state drivers license.
By the way, that German (EU) drivers license is valid throughout the EU. However, you cannot trade that German drivers license for a UK drivers license. The UK will not accept an EU license issued on the strength of a non-EU drivers license. Thus, while any other EU country will accept it for trade, the UK will not. If you want a UK license, prepare for the entire test process just like a new learner. They even have a big sticker with a large red "L," for "learner," to place on your vehicle while doing so.
Hope someone finds this info useful.