Pretty much trial and error. If it gives you the disable option then worse that can happen is something doesn't gel right afterwards. Then you just enable it again if that happens.
Of course I would experiment slowly to make sure as you disable things you give it a little while to make sure there isn't any problems.
Yeah...if you look at the ATT Data Usage...you go to Apps, there are a bunch of various ATT apps running. I don't like the idea of that...especially if they are using my data.