I'm on a Mac myself, and the step-by-step guide to installing
and using Mobi2Mobi
on the Mac are here at the MR Wiki.
It's really a matter of installing the XCode Developer Tools from Apple, then doing a lot of downloading, unpacking, and typing "./configure; make; sudo make install" over and over again. Repetitive and a little tedious in that aspect, but fairly simple.
That said, if you're not technically inclined, Calibre may be your best and easiest-to-use option. It does, however change the entire file by reconverting it every time, even if all you're doing is modifying the author name. But in most cases you'd probably never notice whatever alterations it makes.