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?

centos 5

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