I have finally reached "the" end and want a change? Helpful advice please!?

I have always been one that has struggled with my weight... i was doing really well for quite a few years in my mid twenties and then within 3 years i have had 2 kids, 2 ce-sections (plus one with my first child 12 years ago). i turn 30 this year and i am none to happy about being 45 pds over weight. I dealt with it with a good attitude though but now i am ready, i woke up this morning and just said this is it! i am motivated and lack knowledge! i would like some advice on how i can kickstart a diet, suggestions on a dietary supplement and maybe someone can suggest a great workout dvd.. i would really appreciate helpful tips.. my newest baby is 3 months and i almost lost my life in surgery, i fought hard to be here and i want to make the most of my time here being healthy. Any moms that know how i feel.. how did you do it. thanks