If you are physically able to kneel and carry the altar missal, you should have no problem. Your early acquaintance with the role is a great benefit. You'll probably remember everything in about a half hour of review. Maybe sooner. Take a quick look at the server's responses, especially Prayers at the Foot of the Altar, and the Offertory, just so you won't have any snags. Check yourself on the Confiteor. That's about it.
You're ready!
Remember, altar boys receive a greater share of the Mass graces. Something to think about...