I lost BOTH regulators on my 300E within a year of each other. I've replaced both at the tune of $140 each.
Mine however, broke exactly the same. The plastic sliders on the track disentigrated, and the cable ended up kinked and eventually buggered up at the motor spool assembly. They would go down okay, but would only raise up about halfway. I thought the regulators were reasonably priced, and easier to switch out than trying to surgically rebuild the drive assembly.
The assembly is held in place by 4 10mm (I think) nuts. One at the top and three at the bottom. Once the window is removed from the slider, the assembly can be removed by tilting the top of the track sideways, then carefully removing the assembly out the bottom part of the door. Make sure you have disconnected the electrical connections (of course).
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car