First question- which PSP? 1.50 homebrew will not run on Slims without eLoader or Time Machine, on Phats you need the 1.50 plugin (add-on, don't remember which one)
Second-. Don't bother unless it's one of those firmwares that can be downgraded through Liberty City Stories etc, just grab/make a Pandora's Battery (aka Datel Tool Battery) and make a Magic Memory Stick using ediblebird's thread.