My friends 1997 e420 front ones were out best way to tell is open it up and see. Makes sense the fronts would go out quicker since they're used the most. Its the same process as the rear but easier. Basically take off panel there a video how to on the DIY stickies then drill the rivets out unscrew the window from the metal compress and slip the broken regulator out then put in the new regulator just make sure you align the new rivets where they're supposed to go. NOTE: be careful with the window and the panel the plastic fasteners seem to break easily so pry gently on the sides and have some super glue handy incase.I've never seen one. How do you know it's for sure the regulator? The front ones seem to be pretty bulletproof.
That said, you can sign up with alldata to get the instructions to change the front one, but I'd suggest just getting started. Read through the rear one a bit in detail so you know where to look for hidden screws, etc. Once you get the panel off you'll see how the regulator is held in.
Take pics on your way and do a DIY, gain netimmortality in the stickies.
Anyone willing to upload the diagram for the front on here for this guy? It will make this job alot easier.
