advertising, ah le cart, buffet, on my page

I have ad space set up on my page that currently is not ready to be used yet. It allows a viewer to rent advertisement space in 3 different areas of my webpage. ALthough I want more places for ads. As many as possible, but creatively done not to take away from the enjoyment of the website.. This job was started but not finished..The way it was supposed to work was a customer/viewer/artist would pick a space they wanted to advertise on. Then the webpage would redirect them to paypal to pay for it. Then they would recieve directions on what size the adverisement had to be. and they would need to be able to provide a link so that when they click on the link it would automatically go to their site/product that they were advertising for.. Also they would need to sign up. The ad would need to be kicked out automatically after the week they paid for is over. And I would place my graphic back in its place. All parties would recieve an email reciet of the ad that was paid for .. This whole thing needs to be automated as much as possible. I dont want to have to do much.