hey guys..please don't kill me, but i've looked endlessly around google for the one complete guide that teaches me how to upgrade my CFW, but all seems to be either incomplete or 'maybe' incompatible. Therefore....i was wondering if i can find some help from here.

I have a PSP SLIM on M33-3.90 right now, and no pandora, no magic stick, no extra psp :

1. how in the world can i back up my NAND? just plug the usb cable and copy something from eeprom folder or use some dumping tools??

2. how to verify if my NAND is properly backup-ed so it can recover from disaster?

3. finally, how can i upgrade to the latest CFW?? 4.xx ? any good about it?

any help is appreciated!!

okay, but how to update it properly?? like how to backup nand, then update from 3.9 to 4.xx? i wouldn't wanna risk bricking it since they are so many sifu here