They just renumbered all of the exits... so I can't remember off the top of my head what it will be. I'm thinking it's exit 62 that you'll want.
At any rate, it will be very clearly marked... Just follow the signs for Magic Kingdom, Epcot, Disney MGM Studios, and Animal Kingdom...
The first exit should take you onto World Drive... and then it'll be the third exit, I beleive, that will take you over to the Animal Kingdom area. It'll be marked Osceola Parkway. You'll want to make sure you go westbound... so, if you see the Wide World of Sports, just make a U-Turn (Safely and Legally, please)
In the unlikely event that you miss the first one, theres like 4 of 'em, so you won't have to worry about driving past it... All 4 of 'em can get you to AK Lodge.