Interested to understand what things you tried when it stopped working for you. If you could give us some feedback on what steps you took it would help us smooth out the flow for other users, thanks.
Did you take a look at any of the Site Builder docs at anytime?
If you're going to be building a module, checkout the jrTOS ("Terms of Service") module. Its structure is going to be very similar to what you want built.
It uses "Events and Listeners" to verify whether the Terms of Service have been agreed to and the user must agree in order to continue.
No module currently exists (or is planned) to send newsletters out via PM, but it could be developed if you're up for sponsoring a module to be built for the community.