To start with the passport question, it appears from your post that you live in the USA and therefore, presuming you have a US passport, you do not have unrestricted travel within the EU which is what would be required. You would need to apply for a visa to live and work in Germany. I'm not sure how easy they are to come by but if it's anything like for a Brit to work in the USA it would be almost impossible.
With regard to the language, you will need to take into consideration that this is a German airline and the main language on board the aircraft will be German. You would need to respond in an emergency in German as well as English - do you think you could do this ?!?
There is no harm in applying but I would certainly ensure that you had all the necessary visas etc in place before hand. You will also need to prepare yourself for the expense of travelling to Germany to attend interviews. A better idea maybe to apply for the German bases with the UK lowcost carrier EasyJet - presuming that you could get a visa - as they would have a high percentage of non-native German speakers so it might be easier for you.
Shortm