Hi,
That's alot of information you ask for in one post...would take all day to answer!
First the costa brava is a big place covering an area of around 200km of coastline, what type of holiday are you hoping for, lots of nightlife or a quieter affair?
Sounds like you want to do a bit of sightseeing but Madrid is quite a long way away, would take you the best part of 10 hours to get there.
Info on Barcelona here, this site is built by a British guy who lives in Barcelona-
http://www.barcelona-tourist-guide.com
Debbie