Hmm... this is decidedly non-trivial. One extra thing to bear in mind is that the German spoken in Austria (where I happen to live) is very different from the German spoken in Germany. In addition, there are lots of regional dialects within Austria, so pretty much any 'standard' German word list that you might use will likely not have whatever Austrian dialect words might be in the original German. That being the case, you'll probably need a supplementary list of the dialect terms, at the very least.
If you can tell us which city it is and/or give us a URL, I might be able to offer some further pointers, but it's pretty much inevitable that whatever approach you adopt will be laden with traps for the unwary. Good luck anyway!