LiveCD: How to set rootpassword? Security considerations?

[sleepyvulva at lavabit.com]

When using an Ubuntu LiveCD, everything runs as root or some kind of
ultimate sudo power, right? I have a few questions:

1. How may I change or set a password on the LiveCD during use?
2. If I use a USB stick is it possible to backup the password setting and
other settings? How do I do this? (I'm making my own Ubuntu LiveCD with
remastersys and disabling the use of the hard disk drive for any caching
in favor of using a USB thumb drive for this)
3. Are there any special security considerations for a LiveCD user on
broadband? You're running as a superuser to some degree, right? Isn't
every application running with higher powers now? Is my hard disk drive
data at risk during the time I am using an Ubuntu LiveCD?