My Macbook Air had no sound, and the sound icon was grayed out in the menu bar. After reading about a number of similar experiences I ordered the replacement audio cable from iFixit.
The online guide made the installation a snap. About 35 minutes from start to finish, and the chime sounded when I powered up. It was great feeling.
1. A good set of screw drivers is s a must for this type of job. I used the Pittsburgh - Item #93916, along with a spudger.
2. I used a simple piece of paper with circles for the screws as I removed them (see picture).
3. Use the slide show feature so it fills the screen for easy viewing.