Make URL changes after installation?

I’m in an Ubuntu environment with WP.3.01
I set up WP 3 to work in a multisite environment with subdomains. I am behind a firewall on an internal network. I am not our org’s Network Admin, so I do not run my own DNS, rather we have only one DNS server for the whole org.

I believe I made a mistake when I set up the network, though, and I wonder if I can correct it easily.

During the network setup, in the Server Address field, I believe I should have entered a server address like ourorg.local
Instead, I entered the actual IP of the computer, 10.1.90.XX (I misread the directions.)

On the face of it, the install seems to have worked, but now, I can’t get a pretty address, like library.ourorg.local, or residence.ourorg.local
Instead, new sites appear as library.10.1.90.XX
I would like to get this resolved as we want to NAT some of the subdomains outside as well, and I don’t believe we can put them outside in this format.
I tried to edit the line
define( 'DOMAIN_CURRENT_SITE', '10.1.90.XX' );

in the wp-config.php file, replacing the IP with ourorg.local

After restarting Apache and Network Services, I was unable to reach the site at all due to an error in redirecting.

Is there a simple way to rectify my error by editing files?

Thank you!