Check these links==>
1. http://www.websitetoolbox.com/tool/mb/promod
2. http://forums.maxconsole.net/showthread.php?t=36980
Downgrading is no big deal, u juz hav to be careful or else like e46m3 said, u risk bricking it. Follow the tutorials steps carefully. My PSP FW is 3.30oe'. Get a 2GB or more capacity memory stick duo n u can play downloaded games frm the memory stick.