If you want cardio endurance, a little weight training and a lot of cardio training will do the trick.
One of the key elements of cardio training is building a base so you don't run out of fuel. The other element is to increase heart strengths. Build build a base so you can increase the strength.
A great way to effectively do both is to use a heart monitor. Too many people do cardio too long at hogh levels when there is much to be gained from lower levels - as in base-building. Here are links to two articles and a link to a zone training heart chart. The second page of the chart helps you understand how to use the chart.
http://www.lifetimefitness.com/modul...ning_chart.pdf
http://www.duathlon.com/articles/1460
http://www.trifuel.com/triathlon/tri...ate-000574.php
Good luck!