Personally, I would run all new wire, an new supply line from the vacuum Breaker to all of the Back Yard. I would even redo all of the Back System. It is not going to be cheap, but one pill is easier to swallow compared to all of the leaks, and problems that will arise after you reconnect to the existing back yard, and dead new landscape that you will want after the pool installation.
In my Experience a pro usually will charge between 1200 and 1500 to redo most back yard pool systems.
Good Luck.