You make it sound like your original box version is broken, but that may not be an issue now. If you install Knossos, it will first ask you to point to the folder of your FreeSpace installation. It will then download and set up your FreeSpace 2 Open builds (basically: the modded .exes with the tons of new features implemented by the Source Code Project) and let you download user-made mods as well. These include the aforementioned MediaVPs, which are the graphical updates.
Since you asked about OpenAL: It is mandatory, and I think Knossos instalsl it automatically. If not, just Google OpenAL, click the first result and install it. It takes a minute.
Once you've successfully installed FreeSpace Open (abbreviated FSO) and the MediaVPs (MVPs), then select the MediaVPs as a mod, then click Play. If it launches and you see a non-2000-quality GTF Ulysses in the tech room, then you're good to go.