Richard -- no need to apologise! I'll be happy to answer all of your questions.
> What language is the *Italian* "Divine Comedy" published in? If I take a
> course in Italian will I be able to read "Divine Comedy" directly or will I
> need a special dictionary? Is the Italian of "Divine Comedy" accessible to
> all Italians? Do the dialects have a written version that is essentially in
> competition with the official Italian.
The Italian of the Divine Comedy is that spoken by learnt aristocratic people in thirteenth-century Tuscany. Well, if I take a course in English, will I be able to read Chaucer directly...? :) Italians can understand Dante's language. But sometimes he created new words or used latinate expression or words that don't exist anymore. You'd need no special dictionary -- there's a very good dictionary of the Italian language called Devoto (it's the author's surname), where half of the examples of the early uses of terms are taken from the Divine Comedy. The language itself is accessible to most Italians (those who have a good high school diploma), but the meanings are really hard to understand sometimes, especially in the Paradiso cantos. Dialects do have written versions -- there's a very famous playwright from Padova (Veneto) called Angelo Beolco but known as Ruzante who wrote so many funny theatrical pieces. They are still performed here in Veneto but also all over Italy. He lived in the sixteenth century. In the nineteenth century, G.G. Belli wrote so many sonnets against the Pope in the Roman dialect that's still spoken in Rome. Trilussa is worshipped in Rome as one of the best dialectal writers ever. He lived in the last century. Yet, theirs is not a 'competitive' way to oppose Italian -- it's simply a way to describe the reality they live in through the words of common people. Dialects often happen to have terms which are common in the everyday life of that area where they are spoken, but have no parallel term in standard Italian (simply because it's not needed!).
> Are most Italians bilingual in their dialect and *Italian*. If they are not
> bilingual is it a good assumption that the one language they speak is their
> local dialect?
Yes, most Italians can be considered bilingual. Italian is taught in school and it's the official language. But if you come to a hospital in Veneto, you'll hear the head of the Surgical dpt speaking in Venetian dialect (a friend of mine couldn't understand it, and he came from the region right south of Veneto). If they are not bilingual, it may mean they're rich/aristocratic (that is, they were always taught to speak in good Italian), they've taken up some diction course, they speak in the standard pronounciation you can hear in the tv news (that is, a slightly Roman accent). You can't get away from your local dialect -- even Umberto Eco (who comes from Piemonte) used to give examples of words in his own dialect that couldn't be translated into Italian. Most of the people who're now in their sixties grew up in families where only dialect was spoken and they learnt Italian in school, when they were 6.
Some people living in the country can only speak their own dialect, even though they can understand the Italian they hear on TV.
> What language did the Italian armed forces use during WW II?
The higher officers spoke in Italian. Normal soldiers spoke in their own local dialect -- that depended also on the education they'd received, that is, whether they'd been taught Italian in school or not.