Aerobic Base training and lifting weights???

Hey everyone,
Let me start off by introducing myself. My name is Dale, and have been around the site for a while. I have completed 2 sprint tri's. Once in October 2005 and another in July 2006. I quit smoking in Jan 2004 and went on a weight loss routine in Jan 2005. I am please with the results so far, I have put on a few pounds again, but still work out etc....

I have another friend that has been pretty athletic all of his life, and we were discussing our limiting factors when it comes to running speed. For him its the strength of his legs, for me its my aerobic/cardio. I also made the comment that I feel like my cardio declines pretty quickly in the few times that I have taken a month or so break from any real training.

This started me thinking that I would like to build up my base cardio system over the next few months, so i did some research and found that Aerobic base training is something that is popular. Basically the premise is that you stay at 70-80% of max heart rate for your works outs over a 12-16 week period, never to exceed into an anaerobic state at anytime. Of course this sounds easy, but the hard part is having the willpower not to go above that rate. I know when I am in training mode I tend to stay in the 90% range.

The one thing that I am a little confused on is whether or not I should be lifting weights during this time frame. Since weights lifting is anaerobic, it may actually counteract what I am trying to accomplish with my aerobic base training.

Does anyone have an educated opinion on this. I really want to build up my aerobic base, and would also like to do some weight training, but will the weight training counteract what I am trying to accomplish?

Thanks for the input.
-Dale