When a Clients needs to leave my Multisite Network...

I have a WordPress Multisite network with paid clients.

If a client wishes to leave my network and take their site to a new installation, what is the process for doing this and what should i provide to the client to make this an easy transition.

I fear that it might be a little more involved than merely restoring a WPMU Dev backup to the new installation. but i don't really know. i want to be prepared.

kindest regards,

clyde pearce