Yes, you can flash the latest. The easiest way I think, is Scotty's suggestion of temp booting the recovery and flashing the rom that way. The instructions are laid out very well by Scotty in the thread "How to flash a rom manually". I flashed Nilsp's lastest 4.1 this way and it auto flashes the kernel for you so you don't need to mess with that. Like me, you will also need to flash the old firmware patch. Flash the patch right after the rom finishes before rebooting. Once you flashed the rom, the patch and any "extras" you desire, reboot, and finish following Nilsp's instructions.