Do you know all the in's and out's of your camera and what to do with your lens?

I've had my Canon Rebel t3i for a year now and I want a nice lens since DD's baptism is this weekend but I'm not sure if I have to learn more about my camera in order to use a new lens? We have a decent camera store near by that I'm hoping will help me learn to use the new lens a little before buying it.