Mass editing WAV files?

[the shirt ninja]

I have about 600 WAV files that I need to convert from stereo to mono in order to get them accepted to the site. Now, I'd like to change/edit and then overwrite all these files at once instead of doing each file individually, or at least do it in batches of like, 50 or 25 files. Audacity lets me do the change to mono on all tracks at once, but it seems I still have to re-export each one of them individually, with no option to just overwrite the source file. Is there anything I can do or any software that allows me to speed up this process?

If you can help me with this please make your answer idiot proof since I'm still pretty new to working with audio software, and also an idiot. I can show you my certificate if you want. Anyway, help would be much appreciated.