Fonty
It sounds like a good plan you've got. I wouldn't worry personally about how many days you will fast, more that your plan to create healthier eating habits comes from your fasting in the long term.
That said there is little danger in fasting for any of us who have large amounts of stored food in our body. There are specific contra-indications which preclude someone from a fast- or at least fasting without qualified medical supervision- but you have stated nothing but overeating and being overweight. Unless you have another medical condition you haven't mentioned or are currently taking medications then seek further medical advice for them, otherwise just continue your research but try and find more positive or constructive evidence for fasting rather than exploring the negative sides of it which will most likely not apply to you.
I can certainly atest to fasting being more difficult when you start out overweight and with bad eating habits. There can be distasteful (figuratively and literally) symptoms arising, some may be bad enough for you to have to break your fast- but they are unlikely to be dangerous in themselves, just very difficult to bare. My personal method for fasting to lose weight this time around has been to fast as long as possible then break the fast and recover first solely on raw fruit, then adding raw salads mostly. Then I return to the fasting process after the usual recovery period, which is the same amount of days as the fast was. This way I continue to cleanse, even if at a slower rate, I continue to improve the quality of nutrition in my body and the stores that I continue to fast on, and I am retraining my body to desire the right foods. That way each fast is a preparation for the next one and each time it becomes easier physically. This has worked very well for me over the past three months. I have not only been fasting half that time, but in between have been eating as healthy as I ever have in my life. My body is getting lighter and healthier as I continue and my fitness level is far greater than it has any right to be considering I still have much weight left to lose.
Here is a free online book which will answer a lot of your questions. Hopefully reading through it will calm some of your worries. It is exactly because our bodies our polluted most of us go on this journey, it is certainly not a reason NOT to fast.
http://www.soilandhealth.org/02/0201hyglibcat/020127shelton.III/020127.toc.htm
Good luck!
Andrew.