New Library, Existing files, & iTunes Match

I had a hard drive die but I have all of my music files backed up to a NAS. I use iTunes Match. My problem is now that I have a new installation of iTunes on the new hard drive, I don't have a library file anymore. I have an old backup of that file, but unfortunately, the hard drive was dead for a quite a while before I knew it, so it's pretty dated. On the new installation of iTunes, my cloud library shows up once I turn on Match, but it of course doesn't know that I have all (or most) of the music on the NAS, so it wants to play all of the music from the cloud instead of the local drive.

Is there any way to make the library file on the computer know the physical files are already present? Can I start a new library, add these files to it, and then turn on match? Is my only recourse to re-download my entire 20,000 song library?

I'm trying to make my cloud library, with all of my play history, remain intact and for that computer to point to the files on the NAS so it plays them locally instead of from the cloud.