Been there, done that! It's easy. They are not really stuck. They are just squeezed flat in place during installation by the exhaust pipes. They are designed to compress and conform to the shape required to seal.
Just reach up in there with a pick, preferably one with a 90 degree bend at the tip. Stick the tip of the pick into the edge of the gasket at its ID and pull out slightly. They will come out.
Also, I seem to remember a small slot at the OD edge of the gasket that allowed getting the pick into the gasket on the OD edge as well.