http://www.pspmod.com/forums/downloads.php?do=cat&id=7
theres a downloads sections for this particular reason.
personally i wouldnt leave from 3.52 M33-4 cuz i think its the best.
theres nothing really new and useful in any of the new firmwares anyhow.
if u had a slim u could use skype, but since u have a fat it doesnt matter.