I did it last April. The trains depart from Plaça Espanya and they connect with either a rack railway (in this case you have to transfer at Monistrol de Montserrat station) or a cable car (transfer at Montserrat-Aeri station; info at http://www.aeridemontserrat.com/home.htm ), that takes you to the Monastery area. Once there, you have two funicular railways to get upper on the hills.

There are combined tickets for the train, rack railway, funiculars, museum entrance, lunch at the self-service restaurant, and even include a r/t in Barcelona metro from your point of origin to Pl. Espanya. All the information, in English, is at http://www.cremallerademontserrat.com/