Replace “inverted commas” with «guillemets»

Help!

I'm translating a lengthy book (ENG->ITA) with lots of dialogue. In the italian translations, dialogues must open with «guillemets», whereas the source text uses “inverted commas”.

For the life of me I can't find a way to use the "replace" function to do this automatically. The specific problems:

1 - The tool seems not to distinguish between opening inverted commas (“) and closing inverted commas (”).

2 - The tool seems not to distinguish (!) between the guillemets («») and inverted commas (“”). Therefore the replacing fails. It might have something to do with the language settings but I don't know how to deal with that.

Any kind soul knows a way to fix this? It's eating up lots of time and my deadline is approaching.

You shall have my eternal gratitude