I've just returned from 3 days in Barcelona.
I flew from Shannon on ryanair to Girona.
you need to take a bus to Barcelona which costs 21euro round trip.The bus takes approx 1hr 15.
We stayed in Eixample area of city in hotel Cram which is a nice spot and only a few minutes from heart of City.
Prepare to walk quite a bit but its still not going to kill you.
We did the bus turistic and travelled the 3 routes over 2 days which cost 27 euro for 2 day ticket.
Lots to see and do but the segrada de familia is an absolute must.
I hope this helps a little and would gladly answer any questions asked......