With respect to
http://www.infopop.com/ubb_support/support_ubb_transfer.html ...
1 through 6 is the tough part, and is not version specific.
(Are the URLs the same?)
Then just go into the CP and set the settings as required - I'm 95% sure you can do this without editing vars_config.cgi manually.
I'd suggest doing a dry run first to make sure you can do it easily enough, if feasible..
NOTE: Transfers are installs and questions beyond high-level stuff like this belong in UBB6 Installs - UNIX.
Graeme