I wrote up this overview of FVM few years ago. Sorry for the poor quality of equations on that page; haven't switched that article yet to MathJax. Hopefully it helps. Also, if you are looking for a meshing program, Salome is a good option.
Salome is distributed without the meca bit from http://www.salome-platform.org/, while salome-meca is developed on top of this platform by the Code_Aster guys. I guess you'd use Salome on its own if you only wanted to use Code_Saturne.