MusicEnthusiast,
There are many great places to see in Japan but it depends on how much you want to travel. Are you planning on staying around Tokyo? You could easily spend your entire trip in Tokyo and not be bored but if you have the time and the resources, I would recommend getting out and about. Fukubukuro (lucky bags) are fun but it all depends on the store. Some stores have great deals and some stores have some lame ones. Some people here say that the stores put in things that didn't sell well from the previous year in bags and call them "Lucky Bags" but I think it depends on the store. I never buy lucky bags from a clothing stores. Other people swear that the lucky bags are the best thing since sliced bread.
If you are going to travel around a lot, get a RailPass. It will let you ride any JR train, bus, ferry, or subway for free (even the Shinkansen but you can't ride the Nozomi). That time of year is a busy time and most places will be incredibly crowded so you might want to pay little more and get a reserved ticket, if you can.
Near Tokyo, Kamakura is a great place to go. The town is nice and there are many interesting temples and shrines to see (the Kamakura Diabutsu is wonderful). If you have the time and the money, I like Miyajima (a small island in Hiroshima Prefecture that has the Itsukushima shrine). Also Kyoto has so many wonder places like Kiyomizu dera, Fushimi Inari, and Sanjusangen-do just to name a few. Near Kyoto you can also easily travel to Nara, which has many wonderful sites and Osaka is also not too far as well.
Good luck, I hope that you enjoy your trip.