Upgrading the Ubuntu Server release

Edit: I have just found this documentation article and will be reading it. Is there anything more I should know? I'm looking forward to this, but worried about things that could go wrong.

Greetings,

There are two big production servers running Ubuntu 10.04 LTS, both with Virtualmin Pro, that I'm looking to upgrade to Ubuntu 12.04 LTS. I get the impression this has been done before, so I wanted to get some opinions from anyone who might have experience performing this task. have three questions:

1. Is there anything I should know?
2. What can I do to prepare for the upgrade?
3. Is it safe to run the OS's native upgrade utility, or do I need to have Virtualmin do it all by itself?

Thank you very much!