George,

Had to replace mine last summer. It's a piece of cake, but patience is suggested, because you're hand and forearm must reach (inside the door) to secure the guide with a allen screw.

The window must be up. Remove the door panel. Remove the black plastic cover you mentioned. Look in (with flashlight) and you'll see the guide where the top and bottom portions come together. This is where it separates. Reach in and move the bottom portion. I should wiggle if the guide is broken. Gently pull down on the guide and it will pull apart. Notice how the rubber slides together for the installation of the new part. Guide it out of the opening.

Next, locate a small screw south of the door latch. This screw is what holds the guide in place. Put your hand back inside the door and find the nut and begin to remove the screw. A broken metal piece should be welded to the nut. Remove and discard.

Note: This part had a change in design from the original. My new guide did not have the nut welded onto the guide. I was able to use the same screw, but had to purchase a nut from the dealer to finish the job.

With the new guide and nut in hand, find a piece of duck tape and secure the nut directly over the whole on the correct side of the guide. Drop the new guide into the door, align and push up to meet with the rubber on the upper portion. FYI...I couldn't get the rubber to slide together on my first or second attempt. I thought I was doing something wrong. Look at the end pieces and you'll see how they fit like a puzzle. When you've got it into the correct position, take the screw and secure the guide with the nut you just taped.

Test the guide before you put the door panel back, by moving the window down very slowly or in short bursts. Look inside the door as the window moves. If you secured the new piece correctly, it should move very smoothly. If anything is wrong, move the window back up and repeat the process.