GM (and almost all car mfg's.) have gone to the cable/nylon track/motor window regulators for at least the past decade. They are cheaper to produce and lighter in weight than the old steel track/regulator assemblies (that rarely failed).
If you fail a motor only, you're in luck. You can replace just the motor if the cables and regulator are still serviceable. Otherwise, you have to replace the entire assembly. You have little chance of rewinding that sucker and making it work with any kind of longetivity. The usual scenario of failure on them is for the window to fall to the bottom of the door with the cables in a big snarl.
I've had to do all 4 on the Bonneville over the course of the last 3 years.
The big box they come in says 'always use genuine GM parts' on it. In the corner it says "Made in South Korea"