lol nice picture vonskippy.
He's right linode + cpanel not a wise idea.
Webmin is less intrusive but personally I'd say you're better off just following the linode guides.
On debian/ubuntu here's some tips
1) creating subdomains and domains, I assume you mean in apache, just add another virtual host to your sites folder in your apache configuration then restart apache
2) create users/groups
Code:
adduser username
Code:
addgroup groupname
easy
3) emails...can you outsource to say google apps? it's a darn sight easier. If not, exim + dovcot are your best bet.
4) databases..
Code:
apt-get install mysql-server mysql-client
and if you reallllly have to install phpmyadmin (just remember to restrict access to it).
5) Install wordpress...easy follow the instructions on the wordpress site
6) Monitor the system, check out monit
7) update system/programs
Code:
aptitude update;aptitude safe-upgrade