[RobertWild]

First thought is: Good luck, and may God have mercy on your soul.

Second thought: Prioritise the databases. And then some. How you do this is largely up to your userbase, however I'd probably start with the largest/most complex, and move through the list. Generally you will run into 1 main problem with this - either the departments want to merge in, in which case everyone will think that their system is #1 priority, or else nobody will want in, in which case you will have significant problems even getting decent specs.

Probably the biggest piece of advice, having done something similar for less departments - is to a) find out what each and every flag is for in each and every system that you are about to fold into RE (you may be able to combine different flags from different departments into the one attribute table for instance), and b) map everything out before anything is imported.

It will save a bucketload of time later on.

You will have problems with duplications. Everyone does. Even with CEO's records, where one department mails to the office, the other mails to the home, and of course, neither record is flagged as a CEO.

Maintain working backups of each database you are about to fold into RE for a while after integration. There's always that one little flag somewhere nobody told you about that has turned out to be mission-critical to the organsiation.

Invest in a good stress reliever. It pays off later.