I'm guessing that you just bought this iBook?
You said this iBook is yours, yet you also say that the firmware password is enabled, and apparently you don't know what that is.
Even if you replace the hard drive, your computer will still be unable to boot. That firmware password is not on the hard drive.
If you forgot the firmware password, then you have to reset your iBook firmware. There is a way to do that, and maybe someone else who knows will help you. Apple will help you, but you have to prove that the iBook belongs to you.