I wasn't sure by your post if you were there now or are getting ready to go!
As far as the fireworks, it kind of depends when you are going. When we went in 2003 the fireworks show everynight was "Fantasy in the sky" We loved it and the kids wanted to see it EVERY night. The music was upbeat and entertaining!
When we went back in 2005, it had changed to "Wishes night-time spectacular:" At first we were disappointed because we loved F.I.T.S. sooo much. As the nights went on, we fell in love with it as well! The music is great, the fireworks are un-believable and it is so well choreographed!! Again, we caught it every night!
Our trip 12-30-05 through 1-8-06 was great and this is what I mean by "it depends on when you go!" Because it was a holiday, we saw 3 different shows. At 7:00 p.m. on 12/30 and 12/31 they did the Christmas fireworks. At 8:00, they would do Wishes and at 11:00 or 12:00 the did Fantasy in the sky! (New Years Eve fireworks are something you have to see to believe and is yet a seperate show)
Anyway, the general rule is this: During normal operational times, they will do 1 firework show per night which is currently Wishes. It should be changing to "Dreams" in October. During Holidays, where the parks are open late, they will add a Holiday show (i.e. Halloween fireworks, Christmas fireworks or special Pirate & Princess firework show from 1/07-3/07 only for those purchasing the Pirate & Princess tickets which is a private party just like Mickey's Not So Scary Halloween Party and Mickey's Very Merry Christmas Party)
I may have confused you even more! If you can tell me your dates, I could tell you which ones you will see. Also on wdwinfo.com, you can pull up a calendar which will show you the fireworks. Just remember all are great and worth seeing everynight. It becomes a thing, where you can't end your day without them. Also, when you are at MGM, make sure you catch FANTASMIC!