Terry, for cardio, I'd suggest intervals... carefully set up. First week, 15 minutes daily of walk moderate pace (55 seconds)/fast walk (5 seconds). Second week, 15 minutes daily of walk moderate pace (50 seconds)/fast walk (10 seconds). Third week, 15 minutes, 30/30. At that point, switch to a treadmill, and do 55 seconds fairly brisk walk/5 seconds, jog, maybe twice a week (just walk the other days). And so on. If you do it very, very gently, your body will accomodate the increased intensity without objecting too much—it's like with a pulley: the distance you lift over increases a lot, but so does the weight you can lift. With a graduated approach to intensity, it's the same kind of tradeoff: you take longer to hit your stride, but you're able to go a lot harder when you get there.
At the end, if you can do a medium cardo work out maybe twice a week, 50 seconds jog/10 seconds faster-than-jog, and do serious walking workouts at least three other days of the week, you'll be unstoppable come test time.
