well, it depends on which psp you are getting. currently the only ones that can be fully hacked are the psp 1000 and 2000.
the psp 2000 with the TA 0083 v3 board and all psp 3000s are unhackable using the pandora method and you must use chickHEN to play isos. if your firmware is above 5.03, then it is no use to even try using chickHEN until a newer version is made. (for 2000's with a TA 0083 v3 board and 300x's)
the psp go has CFW, but it hasn't been released by typhoon (they said that they won't release it).
if you're getting a phat or 2000 you can use the pandora method or there is another way... i'm unsure of this method, but you can hack a psp without a pandora battery. and you will need to make a magic memory stick as well. and if the firmware of the psp 2000 is above a certain one then you can't downgrade it, but the psp phat can be hacked no matter what (i hacked my friend's and he had 6.10
)
the 2000's with the TA 0083 v3 boards need to use chickHEN as with the 3000 also, but like i said, if you're firmware is above 5.03, then you can't use chickHEN at all.
(if any of this is wrong, then just tell me, i think i got everything right?)
i use a dual adapter memory stick for my psp 2000, you stick 2 micro sd cards in and it uses it as one. up to 32 gbs on each micro sd card.
and the largest psp iso/cso that i have is a little under 2 gbs...
eternal eyes is a good rpg once you convert it from psx to psp.