The different areas are really fun to explore around Dublin. I would highly recommend doing the Guinness Tour and going to the factory. Book ahead if you're going over St. Patrick's day weekend.
Going to the Temple Bar area is a must, and definitely visit Trinity College of Dublin! See the Rugby Stadium, and if you're still looking for things to do, Dublin has a great convenient bus service that busses people out to the other coast of Ireland daily.
You need to go the weekend. I promise you will not regret it.
Ireland specializes in amazing pub food. Eat it.