Re: Weight loss while breastfeeding
You might want to start by checking out this book: http://www.amazon.com/Well-Lose-Weig...4105555&sr=8-1. It's a great resource on nutrition and weight loss for nursing moms.
Most moms can safely diet and exercise while nursing. Dieting generally does not impact supply unless a mom is starving herself and becoming malnourished. Exercise is a little more tricky, mostly because if you are doing anything more strenuous than walking you're probably wearing a sports bra, and they often hold things in place by compression. A tight-fitting or ill-fitting bra can cause plugged ducts or reduced supply, so before you commit to exercise make sure you have a really good bra. A new bra is probably a good idea, since you may have changed sizes since the last time you worked out.
I don't think 30 minutes of cardio and weight is too much- a lot of moms around here do the 30 Day Shred and it works out okay for them.
ETA: the PP beat me to the punch and recommended the same book I did!
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"