Calories and cardio are inversely related; in that I mean, you can either eat less or do more cardio. They are essentially the same thing (ignoring cardiovascular benefits).
Adding more and more cardio WILL affect your recovery, and subsequently, will cause a loss of strength in the weight room after a certain point. Where that point lies is a completely individual thing. Read WarLobo's "when 30 + 30 does not = 60" on the woman's board to get one p.o.v.
Doing cardio in the morning before eating of directly after your weight training session is best. If you're doing cardio after lifting, I wouldn't suggest doing more than 30, however, because you'll be flirting with cortisol. You need to eat within an hour of completing your last set of weights.
Personally, I think mixing up intensities and duration is best. One day, go long and slow in the morning; another, go medium intensity (~80% of MHR) for 45 min; another do 20 min of intervals (bursts of 1 min at highest "comfortable" intensity followed by a recovery period) with a good warm-up and cool-down. Use different machines every day so as not to get bored.
Other than that... search the boards for more specific diets, etc.
Hope I could help.