I have a piece of tubing I run through the frame with the current cable. Then I pull the cable out and the tubing remains and I thread the new cable in the tubing. Then run the housing it is easy and I don't need anything they offer as a tool to do this job. My favorite though is my regular Ti bike that has exposed cables and I just change them in a flash and much to be said for the old way. Once you have the system down for what your bike requires it is at least doable and no need for anything special you cannot make yourself, and no need to see the LBS.