Is it completely insane?

Nup... you are asking the wrong group of gals if you want any other answer.

I can't get the link to open - so how far away is this ride - as in how much time to you have to prepare.

If you can ride for hours on a bike - with or without stops, then you can achieve this.
You just need to set yourself a realistic goal - to set yourself an unachievable time goal would be the crazy thing.

Do you have people to support you/ride with you, because this can make a huge difference on very long rides.

Centuries aren't my forte, but as long as you have time to prepare and set yourself realistic goals, you are not insane at all.