You need to install several Perl modules in order to get online quotes. While the error message may be about Finance::Quote not being installed properly, that module alone is not sufficient. If it has been installed on your system, the script gnc-fq-update may be used to install the modules needed. That script, as of 2.4.0, uses CPAN to install:
Then read the instructions.
Warning About Open Files
Updating quotes will modify the GNUCash file/database. As multi-user access is not supported (as of 2.4), the file/database should be closed prior to updating quotes.
cron and Non-X Usage
If you attempt to run
gnucash --add-price-quotes /path/to/file.gnucash
without dbus running (for example, from a cron job or ssh without X forwarding), you may get errors such as
GConf Error: Failed to contact configuration server; the most common cause is a missing or misconfigured D-Bus session bus daemon. See http://projects.gnome.org/gconf/ for information. (Details - 1: Not running within active session)
One resolution for this, courtesy of SyncEvolution - The Missing Link, is to launch dbus for the duration of the quote retrieval with a cron command similar to
env `dbus-launch` sh -c 'trap "kill $DBUS_SESSION_BUS_PID" EXIT; gnucash --add-price-quotes /path/to/file.gnucash'