Month in Italy Novice

[Effendi]

First suggestion: buy it in Italy, not on eBay.
I don't know where you are landing, but I think there are no Wind shops at any airport in Italy, so if you want to buy a Wind card, you won't buy it there. You need the "codice fiscale" at any shop you want to buy it, but it's really not a problem to get one, just follow the istructions on that page you already know.

I live close to the Cinque Terre and I use Wind. There are some (very small) places along the walking paths between the 5 small towns that are with no coverage, Wind, Tim or Vodafone it doesn't change, the coverage is not 100% with any of the 3, but it's overall good for all three operators. So go with Wind and you won't have problems, also I think you don't need to be with coverage at 100% of your time.