You can as well download yahoo messenger here http://messenger.yahoo.com/messenger/download/unix.html
, but kopete and gaim are both at least as good or better than yahoo messenger.
kopete works best with KDE.
gaim works best with gnome.
Red hat works best for servers. Fedora is close to red hat but more desktop.
suze and ubuntu (and kubuntu for kde) and fedora have their pros and cons. You can try them all with live CD (I don't know if that is true for suze, but I would think so). It is a matter of taste and they are all worthy to download and try ; even if you choose one, you will have the others just in case you feel like changing.
You may also want to have a look at www.distrowatch.com
and get some screen shots and reviews.
Good luck and have fun.