Yeah, look at trip advisor. They'll probably have 3 day guides that will give you a really good schedule to follow if you're interested in visiting the main tourist spots. You can also do a hop-on hop-off tour bus the first day and that will give you a pretty good overview of the city, then you can take notes on places you'd like to go back and spend more time.
Try to eat away from Las Ramblas, where there are lots of tourist traps....in fact the worst one I´ve ever experienced is there and YOU SHOULD AVOID.....Was conned into having a range of tapas (which was appalling) and then slapped with a 160 Euro bill, when it should have cost no more than 20. They have changed the name because it got so many bad reviews....so make sure you don´t go here.