[Phoenix Gamma]

Official Firmware prevents you from running any programs that aren't authorized by Sony. Custom Firmware is firmware that has all of the official firmware functions, minus the lock on homebrew.

By updating to official firmware, you're basically shooting yourself in the foot, and unless your firmware is 3.5 or below (probably lower) you need a special tool/pandora battery to install custom firmware.

Official batteries can either be hard modded, or you can just buy tool/pandora batteries online for varying prices. After that you need to locate the right files to run.

You're going to need to figure out how to do all that yourself, because modding the PSP also means you can run ISO files directly from the memory stick.