Tools for selling and managing banner ads?

We’re trying to set up a community Web site and are on a steep learning curve with WordPress, our selected CMS.

I’m trying to find one or more plug-ins that will allow us to sell and manage banner advertising on the site. There seem to be a large number of plug-ins dealing with placing/rotating/prioritizing/measuring ads, but how does one actually sell the ads and keep track of how long they’re running, sending renewal reminders, etc., except by some cumbersome manual process?

We’re not interested in affiliate programs but in selling ads to local businesses. Ideally, a business could even order advertising on their own, through a registration and ordering process. Is this a custom development project?

Sorry for the dumb newbie questions …