The sellers details is something you can call into your listing if you have used an Auctiva or customised Auctiva template.
The pre-filled words you describe sound like the section headings under which seller details pages are entered if you have supplied text for them.
I use a simple customised template and leave all headings in place and only those I currently have text for actually appear with thier associated text.
The positions of the seller detail sections are set when editing the template.
Seller details is found on the profiles page, create with care as it is easy to overwrite an existing one when saving in a hurry. You are given an edit window for each section in turn. When completed and saved you can select the sellers details when creating your listing and the text fields are inserted in the chosen position as set up in the template you are using.
Re - moving the SG on a live listing. With the configuration of your scrolling gallery set where you want via the SG editor, copy the HTML for it onto your clipbaord.
Edit the live item via eBay's revise item, and in the HTML editor delete the existing SG code and replace with the code on your clipboard. You may be able to see how to just tweak the HTML but it does seem easy to break judging by other posts. Not advisable when a listing has only a short time to go.