"and it's our reponsibility that the engine runs as it should."
We had a similar situation when we ran mainline excursions with PRR #7002. One was scheduled very tight with regards to the engine’s annual work, which included dropping the trailing truck to overhaul journal bearings and hub liners. As it turned out, her break in run was the mainline excursion, 60 per to Philadelphia and back. Talk about some crossed fingers.
Remember, it’s not like the D&S isn’t familiar with steam locomotives and their foibles . They’ve had their own break-in run debugging to do, as well as some pretty spectacular breakdowns. I’m sure everything will be fine.