If you only want to reconfigure the existing ftp server, you don't need to run xinetd. Just add these lines to rc.local:
killall vsftpd
/sbin/vsftpd /opt/etc/vsftpd.conf &
You can copy /etc/vsftpd.conf to /opt/etc/vsftpd.conf and customize as necessary for your setup.
- K.C.