Currently I’m busy fking “.NET Remoting”. I don’t have enough free time to complete the tutorial.
here’s sth you must read further if you want to do more on MSN Add-in.
anyway, they are tutorials also, but has clear-coded examples.

B# .NET Blog : Your first Windows Live Messenger add-in, and another example.
Angelos Petropoulos’ WebLog :Writing a Windows Live Messenger add-in.

see also: Developing MSN/WLM Add-in Part.I