My attempts to upgrade to Jesse (8) did not work at all and all the
information on the net seem old and not current that Buster is out and
jesse is already archived. Anyway, after looking around, I made ddrescue
copy of the current install disk (only 64GB, so easy) first and then
directly upgraded to Stretch (9).
I had to iterate a couple of times looking to fix broken packages, but
at the end, I had stretch working fine. The biggest trouble I had was
dist-upgrade fail as it could not remove some packages. I had to force
remove and reboot before dist-upgrade worked. After that it was very
easy to upgrade to Buster. However there was some hickups with dbus
connections and commands took a long time. A couple of reboots and force
removal and reinstall of a couple of packages, everything worked (I think)
First, let me date myself: My Computer Career began in Aug, 1973. My first Linux was Yggdrasil Plug and Play Linux, the only one I know of, which maintained /usr/src for the GNU Commands, as well as the Linux Kernel.
That said, Wheezy is *way* too far away from Buster! For example, "Update in Place" is likely to fail, because of SystemD changes. (Heck, I had trouble updating Stretch to Buster in Place, but some of that was User Error).
My Recommendation, if it isn't too late, is to Install Buster in a separate Partition, and then copy /home files as desired. Reclaim the Wheezy Partition when you are sure that you don't need it anymore.
Good Luck!
Kenneth Parker