Welcome back!
First, you'll need a Gold Membership to sell on the site.
Second, ads in the sales section need to have a set price. No auctions allowed.
I know you're not allowed to post to live eBay auctions/sales in the discussion forums. Not sure about linking your straight sale eBay ad to your for sale ad in the exchange. I would advise against it. A mod could answer this with more clarity.
Might as well just take the 5 minutes and create your own ad in the respective section. Some people do post that it is located for sale in other places as well and they will usually state that it will be sold by time stamp.
Hope this helps.