I need help marketing an idea on the internet.

Here is my question:

I discovered something by accident and I started doing it in my home town. I invested $60.00 into the idea and within 3 days I made that back and more. Now here is the problem, I cannot cover the whole US with the idea so I want to sell it online. The problem is I do not know how to market the idea. I want to sell the idea for $199.00, but I am not sure if that is too much?

I already put together a lot of information and a step-by-step guide to help people do the same thing and templates. Now the reason I want to sell it for $199.00 is if they charge for the service like I did which is $30.00 they will make that money back within days. So my question is "What would you do to market an idea like this?"

Also as a side note the idea is so simple I really don't know how to advertise it without giving the idea away in the ad?