Just edit /etc/hosts using an admin user.
This problably won't help though as your name resolution is done through netinfo.
You need to add the hosts file to you netinfo db.
If your hosts file is in the format
xxx.xxx.xxx.xxx some_machine_name
Then you can login as root (not admin but root)
$ niload hosts / < your_hosts_file
You have now added you hosts file to the netinfo db.
you can use things like nicl to look around it.
You can take a backup by copying /var/db/netinfo/*.nidb to another dir.

Hope this has helped.

Dobby.