That could be a whole lot of machine to model. It might take years as a detailed static unit, let alone operating.
Youtube has some video of modern ones. One cuts, lifts, removes, stacks, pulls ballast, replaces huge section with ties, welds rail, and reballasts....it has its own track and "trolley" on it's back, lol.
A RR logger named Con Culhane once moved his whole operation over Michigan's Upper Peninsula's cedar swamps in the dead of winter, because the ground was frozen hard, by picking up the rails from behind the train, and laying them down in front of the engine then moving forward, over and over again.
Inspirational?