If you're relisting an unsold item, hit relist on your selling page, then when the box pops up, select to edit. When the lister opens, up the top right should be a link to switch to the advanced tool. When you click on that it will give you a warning about not changing, select to change. The next screen will show an item box, where you'd normally put in the name of the item you are going to list. Under that will be a link. Click on the link. That is for your listing. It should then open it in the advanced tool with all the details and photos there. It may remove some of the item specifics.
It's been a long time since I've changed between the two, so hopefully it is still the same now.
To use the sell similar option, hit sell similar, then click the link at the top right when the page opens. Then follow the above steps, remembering you then need to change the details and photos that you would have changed anyway.
