from the Carson and Colorado Facebook page:
"SP18: The #DurangoTrain roundhouse crew has received the new pistons, which are ready for machine work and rings to be made. We should receive the new piston rods within the next week. The cylinder head should be completed this week as well. Once all these components are in hand, the team will complete the final machine work and reassembly, with a goal of using SP18 on several work trains in June. We are looking at dates in August to reschedule the canceled trips, and we will also likely add a photography train."
So it sounds like they are making progress.