Mrs G
You can make a separate request for the information, but if you appeal you will be sent all of the documents used in the Decision any way.
If you still want to make the request now then you can contact the DWP office dealing with your claim, there will definitely be an assessment report, there may be other documents if the assessor contacted your GP or other medical support, but it would be unusual for the assessor to have done this.
We don't have a template letter for this, you can phone or write.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems