I/O errors

It looks as though my HD is going bad. For about a couple of weeks now I've noticed that if my iBook (G3) is on for a long period it'll start making this clicking sound and eventually thereafter hang. The only solution being to let it cool down and reboot.

Well, Friday it started saying that it lacked space on the startup disk although I had over 2 gigs. Today, it took much longer than usual to boot and applications are taking a long time to launch. So I ventured into the logs and there I see in the system.log:

kernel[0]: disk0s3: I/O error

disk0s3 is mounted as the root directory and I have no other disks on the system really. (there are 2 /dev and a /.vol, /Network, /automount, ...)

which is repeating about every 30 secs.
Looking back in the logs however, I couldn't find any other such errors except for today. But then I only went back about a week.

I have backed up most everything, so I am not worried about whether I lose the HD or not, but I would hope to save it somehow. What are my options?

Seems like there's a boot disk solution. That is, insert the boot disk and enter a command console and from there do something like fsk.
There is no remedy for a failing hard drive, as the clicking and hanging symptoms indicate... it's a hardware problem, and requires a hardware fix. More than likely, some mechanical part of the hard drive has reached the end of it's life and needs replacing -- since you can't replace individual parts of a hard drive, it's a complete hard drive replacement procedure.

If it is indeed a software problem, you can boot from the OS X Install CD and, when it asks you to select a language for installation, select "Disk Utility" from the "Installer" menu and run a "Repair Disk."
Using the Disk Utility from the Startup disk is exactly what I've already started doing. Unfortunately, I did verify first and it found problems. Then I disk repair and it says it repaired the disk. So now I did verify again and here's what it says:

Reserved fields in the catalog record have incorrect data
Keys out of order
The volume OSX needs to be repaired
(which was the same errors it gave after the first verify).

Does this mean my HD is hosed?

Now I have it in single-user mode and am running fsck -fy. The error it is giving is:
I/O error
Invalid sibling link
(4, 22793)
** Volume check failed

Well, I think then I am going to restore my computer. As I understand from various forums, given the severity of the problem, I shouldn't just reinstall, but reformat my HD. Currently, just to be absolutely certain I have everything I am backing up everything under /users/ . Is there anything else I should consider backing up?
Also, once I get the new system installed - how do I go about restoring mail, in particular. Just copy the files back over?
What about Address Book?
Also I've been using a program called CiphSafe for passwords. Does anyone know whether it will have no problem with my CiphSafe file, or do I need to do something special in order to use it on a new computer?
OH! And what about Keychain? Is that going really get wacked? I guess I can just reset it up.