Easy upgrade on Cpanel *without* downtime

Hi.

I have googled and googled for good, simple instructions to upgrade
from 8.2.3 to 8.3.3 (latest stable at this time?)

I am on a Cpanel interface. Use Apache and PHP for most of my websites.

This seems to be the most often quoted resource on forums etc:

http://kb.linuxnetworkcare.com/node/21

But this suggests backing up, then UNinstalling (downtime and loss of
settings!), then REinstalling postgresql.

Is there no sensible way of simply upgrading the database engine
without affecting either the uptime or the data itself?

I really really do not wish to backup gigabytes worth of data and then
reupload it back into the DB. This represents a downtime of *at least*
an hour or so, which our busy website doesn't have.

Any thoughts or pointers?

Thanks!