Not knowing the steps involved, I am curious how long it took to remove or install an SSME (Space Shuttle Main Engine) in real life.
In the Orbiter Processing Facility (orbiter horizontal) it took, at the end of the program, "less than 4 hours" to install all three engines1.
Good pictures here
On the pad, it took longer, 3 or 4 days, at least in 1999. "Shuttle engines have been changed on the launchpad several times in the past and generally it means a three- or four-day delay. "
1 Wording slightly ambiguous. Could mean a single engine but previous sentence refers to "a set".