It would depend on what is broken. If you can get into the initramfs based recovery mode (keeping <Enter> pressed during boot-up, for a much longer time than is needed with Vol- and the USB downloader mode), the kernel is intact and you should flash a rootfs. It must be flashed to 0x003C1000 - and it will take a long time, so make sure the battery is charged (I think it will charge most reliable when being in the above mentioned recovery menu). You can find a 3g rootfs image in the downloads linked from the sticky recovery thread. It worked fine for a non-3g, wifi-only K3 for me.
If the kernel is not intact, you should flash that. Kernels go to 0x00041000, and you can get them by e.g. using yifanlu's or seanikos rescue kernels. I'm currently not aware of an image of a "pristine" Kernel.
I would need more information in how exactly it is "broken" in order to tell more.