Hi Nicki,
You really must be excited for your vacation! I love Walt Disney World and hope to return there soon.
Since I am not sure which airline you are flying, I can only give you general information. Some airlines will send you an email confirming your reservation. It includes your confirmation number and will tell you basic information such as flight time and seat assignments. It may also tell you what food service they will offer in-flight as well as any fees. In addition, you may receive an email that lets you know you can check in for your flight which is usually 24 hours ahead of time. It will also allow you to pay any fees at this time as well as print your boarding passes. I highly recommend doing this ahead of time so you have less to worry about once you are at the airport.
However, as long as you have the confirmation number, you can look up your reservation and make any changes or adjustments to your seats. Simply head to the airline's website and you are all set.
Depending on the airline, you may be able to print the most horrible thing in Disney World-your airplane ticket home:) Simply ask the concierge for help.
Wishing you a magical vacation!
Beth