Rijeka airport is on the island of Krk. Train station is in the centre of the town. I think there is 30 km distance between.
But, I do not know, but just believe that there is a bus service which will take you there.
In fact, I googled it, I'm sure now
http://www.rijeka-airport.hr/how.asp
"Rijeka Airport provides transportation by Autotrolej buses for each flight, from the city of Rijeka to Rijeka Airport and from Rijeka Airport to the city of Rijeka. The journey takes about 30 minutes. Single ticket is cca 3 €. Tickets can be purchased on the bus.
You can also go to/from Rijeka Airport by Autotrans bus, according to the timetable. In addition, you can take a taxi or rent a car."
Good? You do not have to worry about the currency, since euro is widely accepted.
On the site you have the timetable of those buses.
Slovenian Rail Company, in cooperation with Croatian Rails provides service by the following timetable:
Train no. 482 - Rijeka 12.57 - Opatija Matulji 13.08, arrives in Ljubljana at 15.25, so there is 2 hours and 28 min.
Train no 480 starts from Rijeka at 20.45, arrives in Ljubljana at 23.22.
One direction costs 11,60 euros. Return ticket is 18.40. You have euro price under age of 26, costs 16,40 euros.
Note: Slovenia is in Eurozone.
Hope this helps, have a good trip.
Mike
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