1. It was alright I did this a few years ago. Infomation about Christmas stories, tales and that sort of trivia about traditions. We went on Small World and Haunted Mansion to see them with thier themed seasonal overlays. We got special viewing of the Christmas Fantasy Parade. Also a couple snacks and a pin.
As far as the value in it I enjoyed getting on the rides and watching the parade because it was more relaxed and I went when it was very busy. Since you are going in early December it won't be nearly as busy so I wouldn't waste a midweek day one it and maybe a weekend. It's not a tour I'd highly recommend that everyone should do once, but it may be worth a try, I felt rather lukewarm about it. Other tours I found great and are a true must for some people, this one, it's only good for some people, ok for others.
2. Tours can be reserved 30 days in advance and should be because they have limited space. (714) 781-8687
3. It could be mild, it can be cold and it can rain. Check the weather forecast right before you go to know if you need a light jacket or heavy clothing and rain coats.