here is a one-liner setup script!

http://www.reddit.com/r/Bitcoin/comments/1se3zd/how_to_create_a_full_bitcoin_node_in_a_5_ubuntu/

it runs in root, uses the Ubuntu PPA, opens up 8333, sets a firewall, and sets ssh port to default 22.

to upgrade bitcoind from time to time, run sudo apt-get update then sudo apt-get upgrade.  make sure the new version is posted to the PPA first though by Matt Corrallo.