Hi George. Barcelona is lots of fun, tons to see and do. It will save you much time and money to do your "homework" now.
The first language is Catalan but most everything is written in Spanish as well (and usually English). I's easy to manage in English is most situations, but knowing Spanish can be useful. Flamenco is native to Andalucia, most performances in Barcelona are for tourists.
The RS Barcelona guidebook is very useful, both for practical information (how to use the metro, what's open on what days, etc.). You can also buy it as an ebook. It details the top sights and many more, and includes self-guided walking tours.
Use the official Barcelona Tourism website as a resource too. They offer a number of inexpensive walking tours. I've taken 2 and they were both very good. They also sell tours and activities run by other companies. I took one tour that was very expensive and really awful, another that was excellent, so check them out carefully.
Research the hostels now. Start with a website like hostelworld.com. If you want a smaller room (private single/double or even a small (4 or 6 person) dorm room, you may need to book in advance. A lot of the sights are within walking distance of the historic center (Bari Gotic/El Born area), but many are not. You'll use the metro to get around, so staying in the center isn't that important.
For some of the sights, you need to book in advance (they sell out). The top two are La Sagrada Familia and the Palace of Catalan Music tours. For several others, buying in advance will save you hours of standing in line for tickets.
There are several options for day trips - depends on how long your trip is.