Wishful thinking about everyone speaking English in Italy...

You need to go to your Paypal account, look for the Profile tab and select Add or Remove card

If it's the same card number with a new epiry date the change will be immediate and you'll be able to use it without waiting for the 3 digits' code on your next card statement, even though if it's the latter it may happen quickly if you can access it online, the last time I had to do it it took me about ten minutes