Very interesting your discussion here. The only thing what interests me is to change the German way of using »...« to the Swiss way «...». And this is only important in Books written in German, as 98% of books written in English use anyway the typographically wrong "...".
See Wikipedia about correct quotation marks..
But that would probably merit another topic.
I have tried it with «eschwarz's» suggestion search after «»([^«»]*)«» and replace with «\1». That did the job with a book of 225 pages perfectly.
So thanks all again for your help.