Last week, Lloyd Denise Odell (31) was jailed for 15 months after he pleaded guilty to the theft of antique rail parts from the society's workshop in St Kilda last year.
Set up in 1961, the society operates the heritage Ocean Beach Railway in Dunedin and also reconditions historic locomotives and carriages.
Odell sold the parts, worth an estimated $50,000 to a scrap metal dealer for $600.
He was given a key when he joined the society in February last year.
The stolen parts included a handrail, lights and numerous fittings.
Society president Campbell Thomson said the court proceedings had been a long, drawn-out saga and the society was now ready to move on.
Many of the stolen parts were made of brass and copper which meant they would need to be recast, which was expensive.
''When the locomotives were made in the 1870s there wasn't a shop where you could go and pick the parts off the shelf for it, so a lot of it has to be made again.''
Because it was a volunteer-run organisation, the society would now have to find extra funding to replace the lost parts on top of what it already needed to stay open, Mr Thomson said.
Secretary Grant Craig said before Odell's sentencing many members were ready to walk away but they were now motivated to stay on and help the society recover.
Restoration work had been put on hold during the saga. The train excursions had still operated but only on limited days, because of delays in maintaining the track, Mr Craig said.
''We're behind on the track maintenance, which could partly be put down to what's happened. We haven't been able to run on as many days as we would want to.''
Because Ocean Beach was the first historical railway in New Zealand, it had collected a lot of items and parts before they were scrapped by the rail companies, he said.
The whole experience had been a lesson for the society, particularly in how trusting it was, he said
''You think you know what people are like and then this happens and you don't,'' he said.
''We're probably going have to change our practices, which is a real shame.''
