No, you cannot mod your psp as the 3k's mobo hasn't been hacked yet. However, you can use chickhen without the risk of bricking your psp, though. Just don't shut your psp off or you're gonna have to redo it again.
Yes, installing a cfw will void your warranty, but chickhen won't because your system will stay ofw when restarted.
Check the third link in my sig for details.