Where'd you download the mod? If you downloaded it straight from the SMOD archive [http://www11.tok2.com/home/smod/], you should know that version won't function normally out of the box. SMOD40a and older were built with pre-Episode 2 code and with HL2 now using the newer engine, this causes problems. You can use Onemanshow's tweaked archive here [http://www.bsnooch.com/forums/index.php?topic=282.0] if you plan to play the HL2 campaign.
For how to tweak SMOD's features (gore, night vision, so on), I'd rather just point you to the SMOD Wiki [http://smod.wikidot.com/], especially the console command [http://smod.wikidot.com/script:console-command-list] page and the Customization [http://smod.wikidot.com/nav:indextable:customization] index. Is there anything specific you wanted to change?