duck liver or sweetbreads

I love pate fois gras (goose livers) as an apetizer. I have never had duck livers but I have read that they are the poor man's substitute for fois gras. As for sweetbreads used to eat them quite a bit when I lived in Barcelona but here in Portugal I have never seen them on the menu. I don't cook but if I could find some sweetbreads I think I would make an exception and cook up a batch for old time's sake.