Hello, Casey!
Congratulations on the birth of your new little princess!
That's just about the age my little prince was when I first visited Walt Disney World, so you are so far ahead of where I had been at that time! Traveling with an infant is entirely different, as you've mentioned, so here are a few things you should know about now:
Baby Care Centers: Each of the four major parks has a Baby Care Center, with all you need to care for your little one. You'll find changing tables, microwaves for heating up food, supplies, as well as a room for nursing mothers (dimmed lighting, rocking chairs...very soothing!)
Little Ones at Disney Theme Parks: Read this for tips about traveling throughout the parks and resort with your little princess. Lots of helpful information there!
For rides, anything that's not too jarring with lots to look at fascinated our then five-month old.
Baby-friendly attractions include: (MK) Mickey's PhilharMagic, it's a small world, Jungle Cruise, Peter Pan's Flight, Monsters, Inc. Laugh Floor, Pirates of the Caribbean, Tomorrowland Transit Authority PeopleMover as well as parades and Wishes, too; (EP) Turtle Talk with Crush, Gran Fiesta Tour, Living with the Land, The Seas with Nemo & Friends and Spaceship Earth; (HS) any of the shows (although Lights, Cameras, Action! Extreme Stunt Show is very loud) and Voyage of the Little Mermaid; (AK) Live shows as well as all of the walking trails, Wildlife Express Train and Mickey's Jammin' Jungle Parade. All of these are slow-moving, not scary, don't require 3-D glasses and will be just fine for your baby.
Send more questions as you think of them; I'd love to help you enjoy the parks for the first time with a little princess in tow! :-)