I'm basically a mirror of your experience and age but in a different technical area, out of interest where are you planning on getting the contracting customers/clients from? contacts that you've made over the years?
Hopefully as time goes on, and I get to build a proven track record, I might start looking into doing more word-of-mouth jobs than anything else.
I dont know about elsewhere in the world, but if you too are in the UK, I still don't know whether I will be going through an umbrella company or setting my own LTD and handling the paperwork myself (through accountants).
Hope this helps.
Looks like I might have to do something similar, just a bit risky trying to get them first few customers, especially when you have no contracting experience.
Just put your CV out there and apply to 2-3 jobs. See the feedback you get and take it from there. I don't think previous experience as a contractor is important - that being said, having professional experience in the field is definitely very important.