Finally .

For the benefit of the hopelessly curious and anyone who may follow this thread seeking solutions for their own problems, here's what I did. It finally clicked that the permission problems were due to the partition being mounted -ro. So, (as close as I can recall) I did the following:

sudo umount /mnt/hdb6
sudo mount -t ext3 /dev/hdb6 /mnt/hdb6
chroot /mnt/hdb6
sudo vi /etc/group (I think I had to do this)
sudo vi /etc/lilo.conf (made edits)
exit
reboot

Thanks for all of the help.
Darren