2008 audi A8 front seat backrest is loose
 

Hi everyone I am new to forums so I hope I do this right. I have a 2008 audi A8 base. My passenger front seat (backrest) is loose and wiggles when driving. Is this an easy fix or do I have to go to the garage to fix. I do have a cheap workshop manual on how to take the seat out. Any help or direction would be greatly accepted. Any idea how much it costs at a garage. thanks john