I am trying to remove the leather from the driver's seat on my 2005 monte carlo ss. I am able to unhook the retainer under the front of the seat, but have not figured out the retainer on the underside of the back. Any tips or suggestions would be greatly appreciated.

 

Typically with GM Car seats you will need to remove the seat from the Car. Then separate the back of the seat from the seat base.
After that you should have access to all the area's that will retain the seat cover. At least that is how I did mine and a few others that I have worked on. Good Luck.