Couldn't have said it better myself...the only thing I would add is that as far as cardio - Jazzercise may not bring you up to the intensity that you need for BFL (I was an avid Jazzerciser myself in the early to mid-90's). Jazzercise is great but unless it's radically changed since 1994, you won't be hitting 9's or 10's. I'd recommend doing the 20 MAS by the book three times a week, and cutting back on Jazzercise (or taking it a bit easy).
The cardio seems to be one of the 'sticking' points for a lot of newbies on BFL, especially those who are used to doing at least an hour of cardio a day (like I was!). Sometimes it's hard to believe that only 20 minutes of cardio can be effective. Believe me, it IS, as long as you're hitting those 9's and 10's with INTENSITY. The 20 MAS is a classic example of QUALITY being more effective than QUANTITY.
But hey, if you enjoy Jazzercise, don't cut it out - many of us here do other cardio-type things - I ride Hunt Seat myself and occasionally ride my bike (been a while though) along with walking, etc. Just save the high-intensity cardio for your 20MAS.
Good luck and feel free to post here anytime!