How to update a Moded PSP!

I have an old phat PSP. It was moded by a friend who no long is around and gave me his. it is running 3.80 M33-5. How ever I wish to play some of the newer games(I.E Persona 1 and others) So I need to up date it to 5.00 M33-4 or GEN D(1)yet I followed the steps from anouther site and it is not working. is there a very simple place with step by step or any help?!? thank you

It's pretty simple. You just put the update on your PSP, and run it like you would a game.
Which changing major firmware levels, you may need a copy of the OFW to install the correct files. The update will tell you where to put it.http://dl.qj.net/psp/hacks-exploits/cfw-500-m33-6.html

I tired to do it and it said I was missing something and wanted to go to the net to downlaoded so I did. now I have all in my update folder and no idea what I need or dont.500.PBP
DL.PBP
Eboot.pbp
PUPD.pbp
U235.prx
550.pbp