Are you sure that you don't want to remove the regulator and inspect the trolley and see if some of the plastic glides have broken off? You can also clean the regulator maybe put some clean grease on it and install the new cable retainer.
I think that I have posted some pictures of how to use a small vise grip to secure the bottom cable to the regulator and then use a long Quick Grip clamp to gently pull the trolley toward the secured cable then remove the cable end from the retainer and gently release the Quick Grip clamp.
To better understand, what you are doing is compressing one of the springs located at the regulator motor under the rubber boots. These springs keep tension on the whole cable system and keep a cable from jumping off track on the spool located under the round silver cover on the motor drive.
If you decide to remove the whole regulator I would be glad to give you some tips on reinstalling it. Once you CAREFULLY lift the plastic weather guard so you can get to the regulator. Lower the window, about half way down, until you can see the two bolts that hold the regulator to the window. There are two holes in the door JUST FOR THIS. Don't worry about marking the oblong holes where the regulator attaches to the door. If you look one of the 4 holes is round. Take a black Sharpie and draw a circle around the bolt head on this round hole for reference. Woops I guess I got carried away!
BTW if you find broken glides on your regulator I have replacement ones.
Brad