You shouldn't need to know too much about Linux, but assuming you're vaguely computer savvy and interested, you can learn easily enough (I knew nothing about Linux before I bought my 5500 - a few years back now - I like to think I've learned a thing or two on the way :-)
Regarding MSN, I've had it working without troubles using gaim (try a search for that). The only issue you may come across is that Microsoft seem to change their protocol (in an attempt to keep other clients out I expect), I'm not running gaim atm so I can't say whether it's working currently.
One thing to note - the version of gaim for the Z is based on an older version than that for a desktop Linux box - so some of the latest features shown on the gaim web site may be missing. That said, MSN worked fine. I was also in contact with someone at the tail end of last year who was interested in updating qpe-gaim, I'm not sure what's happenen about that.
Look here:
http://gaim.sourceforge.net/ (desktop version)
http://qpe-gaim.sourceforge.net/ (Zaurus version).
Si
