The default user is "root", but there's no deafult password for NetApp filers, they ask you to setup up a password the first time you boot them. Since this is an old controller I assume someone ran the initial setup already, so if you need to change the root password you have to access the special boot menu before Data ONTAP boots up.
To upgrade Data ONTAP to it's latest release is not that hard, but you need to be sure everything is compatible. Everything is documented on http://support.netapp.com, you need client or partner access to view the documentation and download the software.
I don't think such thing is possible, but if it is, the only way I can think it might work (wild guess) is pre-installing Windows on the Compact Flash Card, but as I said, I don't think that's possible.
Type boot_ontap, that's the command to boot the operating system (Data ONTAP), you will need check if it has licenses installed, type license when Data ONTAP is up and running.
You still have to do a lot of research on how to manage a NetApp filer, it is not difficult to manage, but is not something that you can make a brief on a forum post, look for a local NetApp partner to give you a hand.
Thanks for all your help since I'm a newbie to netapp. I'm connecting through the web interface because I cant download the management client since this netapp wasn't purchased through Netapp or a reseller. It asks me for a serial number of the device to allow me to download any software from Netapp.