Here is a guide on how to tell what firmware you are currently running.
There is no known 'security' flaw in any firmware above 2.80 that would allow a downgrader to be made.
Sony do everything they can with each firmware update to increase security and make it harder to run anything other than official sony software.
Its not really a matter of how long it will take to hack 3.03, but more just hoping some smart hacker out there is able to find a way to trick the psp into running unofficial code.
Could be tomorrow, could be months or even years away. Possibly even never.
This is why its so important for people new to the psp to
not upgrade their firmware until they have read up about homebrew.
Sorry I can't provide a better answer than that.