The Classified Ads will be replacing the Shop Center/MarketBuzz.
The ads will last for 30 days, but it should send you an email or a PM when the ad is about to expire, so that you can go in and renew it if you'd like. You should also be able to edit your ad.
The ad contents are part of what gets searched using the new search box, so that will make things easier to find if you are wanting to buy or trade for something. There may be a delay in new ads showing up in search results, but we'll work out the right time frame for those updates.