Newbie Help: Install LMS7.8 in Ubuntu 12.04

Can someone give me a command line walk-thru on how to install 7.8 on Ubuntu 12.04 LTS?

I've been running 7.7.3. I tried to update via apt using source line "http://debian.slimdevices.com stable main" but apparently 7.8.0 is not there. Ideally, I would like to do an upgrade (preserve my LMS configuration).

Thanks for your help.