everytime I try to install ffmpeg I screw everything up so I would love if it was already there and I just had to enable it or something.
What distro do you use?
I recently needed to install that on Ubuntu, and it was a simple matter of:
apt-get install ffmpeg
And same with the php5 module:
apt-get install php5-ffmpeg
However, even with another distro, it shouldn't cause everything to get screwed up -- what sort of problems do you run into?
yum doesn't do that unless you have dag in your repos, but you dont want that as dag breaks your webmin.
so best is to check out the website http://ffmpeg.mplayerhq.hu/
i installed ffmpeg which came with the mediaserver and its also included in the gallery2 script.
if in the end you cant do it I suggest to install gallery2, get the ffmpeg through the script and then delete the gallery again, thus leaving the ffmpeg in the correct place