That’s the link I used to make this happen. Of course, I would suggest using nano to edit the wp-config.php file, that’s about the only thing different that I had to do.
I would also suggest using Server 8.04 instead of desktop if you are looking to setup a dedicated wordpress box. There isn’t a good reason to use the full-up desktop install for this. On top of the wordpress LAMP requirement, I would definitely install openssh. The other handy software install I did was webmin: http://ict-freak.nl/2009/02/18/how-to-install-webmin-on-ubuntu-804/ and this gives a great overview of what is going on.