Price too high
I know that I will probably get some disagreement on this post but I think that they grossly overcharged. Ive replaced my sunroof before in my old 420SEL (same parts as the 300SDL). Breakage is fairly common when they age. I have yet to see one fail in a W124 (fingers crossed). When you replace the mechanism, there is two sides. Each side consists of a rail, which includes the mechanism. Each rail costs about $110 dollars, and is a dealer only part. That was what the price was 2 years ago. Perhaps they could of raised it.
A sunroof cable is about $50 dollars. These parts are tricky to put in, I wouldnt attempt it if you have never had experience with it before. You can easily snap the new rails if your not careful. A good independant mercedes mechanic can do the job in about 2 hours. Mercedes only gives you 1 year parts warranty on them. So after 1 year, if it breaks, your screwed. Ive seen new ones break after only a year.
Total parts should be around $300 give or take
Labor shouldnt me more than 4 hours. All depends if the tech ran into any problems. 4 hours is pretty generous.
As far as the inspection goes...the headliner takes about 30 seconds to pull off. Although if the sunroof isnt broken, you dont need to pull the headliner off to inspect the rails. Its fixing an already broken sunroof that is the hard part. You have to slide it back somehow to remove the headliner then unbolt the metal sun roof. The rails will then come out in pieces. The headliner has to be out to make final adjustments to the roof, in the way it seals and closes. Some sunroofs may be out of time, meaning that when you close it from being slid back, it will go right thru the closed position and right to the pop up, or vice versa. I had a mechanic once that said I need a new sunroof motor to fix this. Pretty ridiculous. There is white wheel in the trunk on the sunroof motor assembly that you can pull out, then turn to fine tune the adjustment. Once you see how it works its quite easy to time. I did it myself, and saved 400 dollars on a new motor (that would have to be timed anyways).
The best advice I could give 126 owners is to make sure the sunroof mechanism is properly lubricated. Lack of lubrication is the primary reason for failure. The mechanism will begin to bind, and shim to one side, and snap parts. The rails are very brittle.
Hope this helps some of you...
93 300D 2.5 Turbo, Black/Palomino 273K
09 E350 Black/Black 41K