I have bought a cable for 20$.
Because of the two sharp turns you have to use your muscles - so be prepared.
The cable has to be very well lubricated whith silicone based grease else it will be slow or malfunction.
Put it in the guide from the roof when you feel resistance you have come to the first turn, just keep forcing it in. Continue with that until you can't do it anymore. You should now hav hit the sunroof motor.
There are two kinds of cable.
Old model: is a steelwire with a spring shaped wire around it. This is hard to put in.
new model: is a steel wire with a lot of nylon bushings on. This is really hard to put in.
I hav heard some people attaching a drilling machine (eletronic speed control) to the end of the wire in order to right hand turn the wire upon putting in, but that i have not tryed.
'85 190E (sunroof change)
'87 300E (sunroof change)