chickhen you will need 5.03 installed if you dont want to use the pandora battery. but other than that 2000 models it deosnt matter what firmware you are on, as long as you have the battery you should be able to get firmware on it.
i installed custom firmware on my cousins 2001 psp. scared me for a while, but in the end it worked. that is the last time i travel without my pandora battery.