Ciao 10 Lire!
If I remember correctly, you must have CivIII classic CD to use Civ III PTW expansion.
The patch is free, so you probably already patched the game, but usually the orginal game is only needed for commercial reasons: the .exe and .dlls will be replaced anyway with different files from the new CD.
So the answers are:
"Will I get a complete .zipped patch available on PTW CD?" Probably NO: look around for a magazine CD or download it with a broadband connection.
"Must I have the Civ III patch to play with PTW?" Surely NO, the game will only check the original for copyright/antipiracy reason.
Both seems good news for you
P.S. Se vuoi far due chiacchiere in italiano mandami pure una Private Mail.