Alright, I assume that you know how to get to the instrument cluster and how to remove it since you didn't ask about that. Pull the cluster away from the dash towards the steering wheel once you've removed the screws and the cable will have a white "collar" that you'll see behind the speedo head. Squeeze both sides of the cable at/on the tabs and pull the cable away from the cluster. It may take some slight "yanking" to get it off because they can be a pain in the a** sometimes. Other than that, you'll be fine.
I was told to push the flat side of the plastic clip. I screwed with it for a few seconds and it came off. getting it back on was a little more difficult, but no big deal HOWEVER, when I went to remove it again I couldnt' move it. I don't know what I did the first time that I was unable to do the second but I would try squeezing the thing, like the earlier post says. I thing I pushed the cable in towards the instrument panel and spun it a little (almost like a prescription bottle).