This video builds on the excellent ‪@fixaday‬ video titled "Evaporator Core Replacement 2004-2009 Toyota Prius" by adding a faster strategy for wire harness relocation, and a tutorial on replacing the heater core.
I suggest watching Wayne's video, then this one, so you have the overall effort in mind before you begin the work. For me, this was 20hrs of work start to finish, spread across 5 days.