Here is the second problem I run into, once solved Proble updating Gentoo

Trying again with this command.

sudo emerge --update --deep -p world

I got this

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

www-client/mozilla-firefox:0

  ('ebuild', '/', 'www-client/mozilla-firefox-2.0.0.19', 'merge') pulled in by
    =www-client/mozilla-firefox-2* required by ('installed', '/', 'gnome-extra/yelp-2.22.1-r2', 'nomerge')
    (and 1 more)

  ('ebuild', '/', 'www-client/mozilla-firefox-3.0.6', 'merge') pulled in by
    www-client/mozilla-firefox required by world


It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously. If such a conflict exists in the
dependencies of two different packages, then those packages can not be
installed simultaneously.

For more information, see MASKED PACKAGES section in the emerge man page
or refer to the Gentoo Handbook.

Solve it adding to your /etc/make.conf in the USE line this at the end

-firefox xulrunner

And then run

sudo emerge --update --deep --newuse world

And it will work.

I found the solution in the Gentoo Mail Archive thanks to them.