You are going to have a blast. Here are some tips:
1. Don't try to do it all. Follow your daughter's cues and take breaks when you need to. If you're constantly on the go and she's melting down, no one is going to have fun. Stop for ice cream or something.
2. She might get sick of waiting in lines, so plan to spend some time at the play areas in ToonTown. There are a couple of mini playground type places with slides and clubhouses that she can freely play in without having to wait.
3. Visit the Baby Center. If you were walking up Main Street from the main entrance, you would turn to the right just after the last shop (where the street opens up to the big circular area in front of the castle). They have quiet places to feed the baby, microwaves to heat bottles if you need it, and really nice changing stations. It is very quiet and peaceful in there. It's a really good place to take a break.
4. Several rides are closed right now for renovations, so don't set your heart on any certain rides. Some are long-term and others are just to get set for the holidays, but just know that some things might not be open (Small World and the Teacups were both closed when I was there a couple of weeks ago).
5. The Storybook Canal, Casey Jr. Train, and Small World (if it's open) are all good rides, as they are slow and not scary if some of the other rides freak her out. A lot of little kids get scared by the "inside" rides in Fantasyland, like Alice in Wonderland, Pinocchio, Peter Pan, etc. She might be fine, but just something to keep in mind.
6. Bring lots of snacks and lots of diapers. Don't leave valuables in your stroller while you wait in line. If you have a common stroller, put something on it to distinguish it from all the others.
Just don't have too many expectations or try to make special/magical things happen. You'll have a lot more fun if you go with the flow and follow your daughter's lead.