Very easy to put the cable in. The spring clip stays there as you can see from the fine picture anouther member has posted. In super easy, out can range from easy to pulling your hair out. Biggest problem really is that you have no room to work or see what your are doing in that confines space.
If the cable leaks oil ( and they all do ) it is not normaly the small o-ring on the cable but oil leaking out of the plastic cable cover through the metal outer cable. Simple case of old age and being perished.