Best information that I have found for training for Tri's:
Trinewbies
If has various training programs for various lengths of Tri's. Sprint, International/Olympic, and 1/2 and Full Ironmans.
Be forwarned, the training for an IM is supposed to be intense. I would recommend that you train for and run in a shorter distance first.
I am current training for the Chicago Tri in two weeks. It will be may second tri.
-Rob
P.S. I met a Triathlete out swimming one day, and he described Tri's as "as addictive as Coke, but only more expensive." I am beginning to believe it.