It probably isn't too difficult. You'll want to follow this guide, or one like it.
http://blog.costan.us/2009/03/ubuntu-810-or-904-on-mac-mini.html
It explains how to install an EFI bootloader. Maybe from there you can get it setup right.
http://blog.costan.us/2009/03/ubuntu-810-or-904-on-mac-mini.html
It explains how to install an EFI bootloader. Maybe from there you can get it setup right.