Is there a way i can build an add on to (MSN) Messenger Live? I heard its been done by something called MSN PLUS but i havent tried it and have a feeling it uses hacky methods.
Yes you can, there is one often used add-on called Messenger Plus (some don't use it because of suspicious optional bundled software).
This looks like a good starting point.
(also, I think Windows Live Messenger have dropped the MSN prefix)