As soon as I put into Reverse the rear goes on continually without beeping. Any ideas

 

Do you mean that you hear a continuous beeeeeeeeeeeeeeeeep when you are reversing?

If so, it is likely that you have two failed sensors-you can pull the appropriate fuse (see owner's manual fo fuse no) to stop the noise until you have sensors replaced.

 

How easy or difficult to replace back up sensors??

 

Not difficult except if you have corroded fastener (wheel arch to rear bumper) you may have to saw it off.

Remove rear bumper (JTIS) and subtitute good sensors until system works.