Any idea how to repair/replace this as it does not look like a easy endevor.
It's actually pretty easy to put a new line inside the tunnel.
Remove all the covers to the tunnel (shift coupler, frame head, body in front of frame head)
Disconnect the shift rod
Remove your pedal assembly, shifter, and e-brake.
Remove one seat (or two)
Get a light bulb socket with nothing around it and stick it in the tunnel at the shift coupler.
Now you can look in from the front and see all the way to the back of the tunnel.
Cut the old line where it goes into the left frame horn and remove it.
Insert a piece of welding rod (or straighten out a coat hanger) into the exit hole of the left frame horn until it comes out by the shift coupler.
Start feeding the new line in from the front, making sure it clears all the other tubes along the way.
When you get the new line to the shift coupler, insert the welding rod into the line. Keep feeding the line from the front of the car while the welding rod guides the line into the exit hole.
After everything is open and ready to accept the line, it takes 10 min to get the line into place.
Then, using super long nylon zip straps, secure the new line to the old one. You can put a zip strap all along the tunnel through all the holes.