I didn't mean to imply that both would be running in tandem, 2008 was placed over 2000.
I patched 2000 up to SP4, ran the Upgrade Advisor which deemed all agreeable.
However, after the upgrade one of the databases was offline.
It appeared healthy in Management Studio, but it had no system properties, no tables, nothing.
Fortunately I had a backup from 5 minutes before the upgrade.
I restored the DB with that backup, 2008 took the restore, and it's been smooth sailing since then.
I hope this information helps anyone with a similar project.