well, that is gnome-schedule,

so +1 on figuring out the right task scheduler.
Apparently, on Ubuntu you should be using
Code:
gksudo gnome-schedule
which is essentially the same program but with a slightly different name (we don't need to get into
why).
It asked you to install gksu in addition, since it didn't have it yet, and was just asking yes/no should it be installed. If you run that command again, and type "Y" and click enter, it will install gksu.
Or try "gksudo gnome-scheduler" which should already be there.
Anyway, you will get update notifications in linux too, it's just why settle for notifications if you can get automatic updates?