"sh-2.05a#" on crashing initial loading screen.

at the sh-2.05a# prompt you could undo what you did by reversing step 6.
You did do step 6 yes? If you didn't then this won't apply. What step 6 did was copy the original and save as a file called hostconfg.old.
Now following the code below replace the changed hostconfig with the original one that you saved.

6. Type

sudo mv /etc/hostconfig.old /etc/hostconfig

7. Press Return.
8. Type the Admin user password, and press Return. (that might not be necessary here but do so if requested)

Now restart and see if it boots correctly.

By the way, the article that you followed applies to 10.0.1 to 10.0.4. Your profile says you are on Jaguar 10.2, so at first glance, I would not have thought that solution would apply to you.

Try replacing the CD drive. Do you have a spare one around?

Right. I see.
restart again then type; following with 'return'

fsck -y

wait until the prompt returns,

mount -uw /

then you should have write access and then

mv /etc/hostconfig.old /etc/hostconfig

reboot

note; I changed line 6 and omitted 'sudo' this time as it should work with that.

Is there anything I need to do now I can log back in...

No, you are back to normal now. The CD drive seems less important now.
Backing up is a good idea. If you have an external firewire drive, then using SuperDuper which is free can create a bootable clone on the external drive. The other day I was playing around with a configuration file trying to get a printer to work and ended digging myself into a hole. So a reinstall from the clone put me back to square one.

I am glad things worked out and thank you for your reply.

You are welcome, and your gratitude was most warmly received. I always find praise an unexpected shock, but you did make my day. Thanks 🙂