Honestly, it didn’t take much to make it sound the way it does, which was good for me because I still managed to do it messily.

My steps:

Cut the audio from the commentary (there’s almost no extra sound in the background of her line there)
Cut the audio from the line in the movie (I ripped my blu-ray) and put the audio from the commentary in.
Add some music back in using the rip of my CD soundtrack and have it blend into the music before and after the line (you might notice the discrepancy if you listen, especially at the end of the line).
Adjust the volume for the new audio sources.

I didn’t even use a dedicated audio mixer, just Vegas Pro 14…

IDK how useful my own work will be, but I can send you what I have if you’d like. It would probably be even easier for your version since you’re just totally replacing the music in that scene.