Newbie assistance



I am looking to get myself motivated to get into shape and would like
to use competing in a triathalon (next summer?) as my motivation. I
was a competitive swimmer in High School and swam in a club year
round.. I ride my mountain bike about 10 miles every other week around
a local lake and play some pickup volleyball, but that is the extent of
my workouts. I also did some triathalon's in High School, but haven't
been in that sort of shape for about 13 years - I've probably put on
upwards of 80lbs since then.

What is the preferred method for getting into any sort of shape for
doing triathalon's? I was at an Olympic sized pool about a week ago
and for kicks attempted to swim 100 meters and just about croaked - my
body remembers the old workouts but no energy...

Any great ideas or expert advice? Any books that are good reads.