Hello sillyship -
In order to make the code usable to post to eBay it will need to be converted to a format that eBay will accept. There are converters available online, but an easy one to use is available at:http://www.isdntek.com/tagbot/YouTubeConverter.htm
This will present you with another piece of code that you can embed into your listing and then post to eBay.
When you are on the one page lister creating your listings, you will need to set the Item Description Editor to HTML mode by clicking on the 'Source' button in the upper left of the editor tools to add this code; please keep in mind that the video will appear in the item description wherever you place the code.
You will be able to check the placement in Preview to ensure that the video appears where you prefer in your listing.