After you've ifconfig'd.....
/etc/hosts (the line corresponding to the appropriate hostname.interface file)
/etc/netmasks (this is a softlink to /etc/inet/netmasks)
Obviously this'll all need to be done from the console....
There are other files that'll need changing depending on your needs and the scale of changes made. There's a script
here for a hostname change if you need to do that also.
It is always worth doing a
find /etc -type f -exec grep "old.ip.address.here" {} /dev/null \;
to see if the IP address appears anywhere else (hard coded into badly written start scripts, or whatever)....
Also; there may be application specific changes to be made, for example, Sybase would need changes to its interface file, etc, etc, etc....
Cheers
ZB