If you want to use "smxi", the sidux maintenance script, you have to install it manually because it is not part of "sidux-scripts" anymore. Read this post on sidux forum for more info. To install smxi follow h2's advise and run as root:
cd /usr/local/bin; wget techpatterns.com/smxi.zip; unzip smxi.zip
I'd strongly recommend using smxi for updating sidux - it's a lot safer! ;-)
Installing erebos is as simple as with previous sidux releases: boot the live cd, run the installer and 5-10 minutes later it'll be on your hard disk and greets you with a new elegant art theme:
If you need more infos on how to install sidux, have a look at this post or consult the very good official sidux manual here.
So, if you're interested, download sidux, install it, have fun!