>Q: now should I upgrade the other Debian packages to jessie?
You should not run Stable and Testing (in this case Wheezy and Jessie) on the same system. If you must use Testing type packages then you are much better off either running a full Testing system or running Stable with Backports if the packages you need are in Backports.
> At what point do I use dist-upgrade?
From the Debian manpage
"
upgrade upgrade is used to install the newest versions of all packages
currently installed on the system from the sources enumerated in
/etc/apt/sources.list. Packages currently installed with new
versions available are retrieved and upgraded; under no
circumstances are currently installed packages removed, or packages
not already installed retrieved and installed. New versions of
currently installed packages that cannot be upgraded without
changing the install status of another package will be left at
their current version. An update must be performed first so that
apt-get knows that new versions of packages are available.
dist-upgrade
dist-upgrade in addition to performing the function of upgrade,
also intelligently handles changing dependencies with new versions
of packages; apt-get has a "smart" conflict resolution system, and
it will attempt to upgrade the most important packages at the
expense of less important ones if necessary. The dist-upgrade
command may therefore remove some packages. The
/etc/apt/sources.list file contains a list of locations from which
to retrieve desired package files. See also apt_preferences(5) for
a mechanism for overriding the general settings for individual
packages."
If there are no new packages (in other words packages not already installed in any version) required you don't have to use dist-upgrade,
if there are new packages required you do have to use dist-upgrade.