Will iTunes Download an Album Twice if I Purchase the Deluxe After the Original?

I wasn't sure how to word the subject line but I already downloaded/paid for an album and now the artist is dropping a deluxe album with the same songs plus a few extra songs. If I purchase the deluxe album, will iTunes download the entire album, including the songs I already bought, or will it only download the songs that I don't have? This goes for payment too. Do I have to pay fo the entire album or do I only need to pay for the few songs that are on the new deluxe album? I was going to pre-order but realized that once the date comes, I might end up buying the exact same album again (plus the new songs, which are the only songs I want). I hope this makes sense. Thanks in advance!