Hello. Could use some help on how to remove and install the lower guide roller on the driver and passenger front glass (pic below). Are these press on or do you have to drill and replace the riveted ball stud?

Motor City Muscle Cars offers a roller that is identical in measurements to mine, but for a 69 Chevelle and Cutlass. I have s 68 Cutlass. They say the roller presses onto the existing 69 Chevelle stud. They also want $25 bucks a pop for one roller, no ball / stud. Anybody know where I might be able to get them cheaper?