i think the easiest way would be to get the train to macanet and change there for girona (you may need to change at Blanes as well).

the renfe site may help.
look here for trains to macanet.
you may need to search a bit further for train times on the macanet/girona part of the route, but the booking office at SS station will sort you out. they speak good english there.
there is a bus from SS in the morning to girona, via the airport, but not one back beyond Blanes. i don't think it goes to the station, but may be wrong.
look here
neither way would be that expensive.

Blanes and Santa Susanna are on the same line so I would not think you would have to change. Looking at the map the rail line goes inland once past Blanes and goes to Girona.

thanks jim and hi de, been promising myself a trip to girona for a good few years now, will defo go this time, i hear it has quite a bit of history to see

Saw a little bit of Girona on a Place in the Sun looked a nice place to me from what we were shown