Just wondering first, do you happen to have a Runescape account
of the same name, then gave it to a friend?
And upgrading PSP should be easy if you're using the 1000/2000
[Not the new chip 2000] version and follow accurately the
details. There's also Youtube guides for them.
I think the all-in-one installer from those google result should
be beneficial since I can't post links.
Regarding whether you can play ISO/CSO from Memory Stick after
changing version, yes you can. Better usually for me, cause
compared to some of my UMD games, loading times slightly faster for
ISO. Then there's those applications and more, that you can add to
enhance your PSP experience.
PS: Or send to shops for modification, it's easier, faster and
usually better than "brikcing" it accidentally. Also, the latest
version is 5.00 M33-6 if I'm not wrong, better to have latest
version cause some games, have their save files corrupted when
version changes again.