Steps I used:
0.  Backup everything
	/etc/krb5.conf
	/etc/krb5kdc
	Anything else...
1.  Stop KDC and any related servers
	/etc/init.d/mit-krb5kdc stop
2.  Make sure KDC and related (like kadmind) stopped
3.  Dump Kerberos database to text
	kdb5_util dump krb-backup.txt
4.  Upgrade to new version
	emerge --oneshot -av mit-krb5
5.  Update /etc/krb5.conf by removing kdc.conf definition
    New default location is /var/lib/krb5kdc/kdc.conf
6.  Move /etc/krb5kdc to /var/lib
	mv /etc/krb5kdc /var/lib
7.  Edit /var/lib/krb5kdc/kdc.conf to change /etc/krb5kdc paths
    to /var/lib/krb5kdc
8.  Delete old kerberos database (in my case called "principal")
	rm /var/lib/krb5kdc/principal*
9.  Build a new empty database (give the command the same database password
    you previously used)
	kdb5_util create -s
10. Load database text file into new database
	kdb5_util load krb-backup.txt
11. Start Kerberos
	/etc/init.d/mit-krb5kdc start
	/etc/init.d/mit-krb5kadmind start
12. Test
	kinit dude@KERBEROS.REALM
	klist -fan