Hi, Stacey! It's so exciting to help someone plan their first trip! I hope it turns out to be a magical experience that you'll want to repeat time and again!
You don't say how old your daughter is, so it's tough to recommend something special for her. I would say up until she's about age 10, My Disney Girl's Perfectly Princess Tea is about as special as you can get! This magical tea party, held at the Grand Floridian's Garden View Lounge, features appearances by Princess Aurora (Sleeping Beauty), and an enchanted rose from her garden, Rose Petal. There are sing-a-longs, a princess parade, and special gifts for all of the children attending, including a doll similar to an American Girl doll.
You can send me another question and let me know how old she is, and I can come up with more birthday suggestions for you!
As for planning, start at
www.disneyworld.com to see where you might like to stay. I like to get the big decisions made, like where I'm staying, what time of the year I'm going, and how I'm getting there, so having the hotel is a big step done for me. There are resorts to fit practically every budget from the Value All Star Resorts through the deluxes like the Polynesian. Decide how many days you are visiting and how many of those days will be theme park days. That will help you choose a package or tickets.
You can work with a travel agent, or contact Walt Disney World directly when you are ready to book. I find the cast members to be very helpful in assisting with my planning.
I hope your vacation is magical, and the planning a big part of the fun!