Patching games is quite easy once you have the patch :
_ ".diz" files are text files (just as ".nfo" files), they often tell you what to do with your patch...
_ ".ppf" files are the real patches.
What you have to do is to apply ppf file to the image it was made for. For that, you'll need a program like PPF-O-MATIC or APPLYPPF :
http://www.megagames.com/psx/psx_ppf.shtml