Sorry to hear that the cable is bad. If you're going to install a new system, I've had good results with one like this from this vendor:
backup camera systemI installed one like this in 2010 and it still works great. Running the cable down the back cap, along the frame rails (protect from heat and rubbing) and back up into the dash area is not too difficult, but does require a lot of sliding around under the coach.
I have a write-up that describes the installation with pictures that I can send to you if it would help. Send me a pm with your email address if you want the write-up.
The system displayed by dale.traveling above looks good also.
Fred