Input of XML documents (input of unicode)

[Torsten Bronger]

Halloechen!

I've just compiled Emacs 21.2.1 on my Linux system.  I've
used Emacs 20 for a rather long time now, and the most
important reason for me to migrate would be better 
XML and unicode support.  But:

1.  How can I input an arbitrary Unicode Character?
    I open a file in UTF-8 encode, and inout C-g
    and an octal unicode number, but always the message:
    "invalid character".

2.  What is the most convenient way to install the XML
    mode in Emacs?  It isn't part of the standard
    installation.  (A pity.)

Tschoe,
Torsten.