Roman,
should be able to tell with a metal clip covering the box that houses the coupler. I usually take a very small flat head screw driver and slide it in on the outside of the box, just a bit to catch it, and just give it a twist. That should free it up. The Kadee's should be an easy replacement after that with a little bit of graphite and some clean up of the coupler end that sits in the box with a file to make sure that if fits in the spring corretly.