About the outer pipe (Cable guide)you can't know. You have to test. The pipe have to very sharp turns one at the top middle rear window and one at the topl
left side of the window. The turns get worn out and there will then be a hole in the pipe and the cabe will get stuck in the hole. The only way to test this to put in a new cable and see if it works.
If you have to change the cable guide.
1. remove rear window
2. remove head lining in the rear and along the sides.
3. You are now able to change the guide.
It is very difficult to put ithe guide in under the chassis and down to the trunk. Be careful not to bend it too much.
Make sure to seal the rear window well during assembly.
(from a country were it rains a lot)
P.S this procedure goes for W124 and W201