LoCarbJ-
I used to do triathlons and a rule of thumb that I learned was that your weekly milegae should center around 3 times the length of that event in your race - and no longer. So, if your race includes a 6 mile run, you would want to do no more than 18 miles a week running. you can stress one event each week to avoid overtraining....a hard running week will mean an easy swimming week, etc.
Another important thing is training yourself to be a really, really efficient swimmer. DRILLS, DRILLS, DRILLS are your friends, rather than laps and laps of swimming with poor technique. You want to be able to swim without using up too much precious energy. When I raced I learned that Im' never going to be able to swim that great in the race (roughwater swimming) so I just wante dto be fit enough, swim-wise so that the swim wouldn't tire me out too much for the next two events, which I was better at anyways.
okay, enough lecturing from me!