Using Membership with Templatic Theme

This is a bit of an out of the box help question. I have a great theme from Templatic that runs classifieds.

I want to only allow paying members to access the post a classified section.

I also want to set up a send email that will allow only paying members to communicate with each other. I don't even know where to start with this part of it.

If you visit the site looking at the pages that are used might give one of you really smart folks an idea as to how I can protect the site.

Membership is disabled at this point so you can see everything in it;s developing glory for the client.