Thanks for help on finding hissing sound of water leak. The hissing sound appears to be at end of water supply to that rear area of house. What is best way to have repairs done on the leaking pipe that must be under the slab? Is it best to cap it and run new water line overhead? Or is it better to repair the pipes underneath? How is best method determined? What type of cost estimates are to be expected for repair? How many estimates should we get?Thanks for everyone's help and comments.

the sound of the leak sometimes is not exactly where the actual leak is. it might be a few feet away under the slab and the hissing shows up where the pipe exits the slab. so, i would replace rather than repair. if running overheaed is an option , that is the way to go.
pricing is not discussed here...

Packy is correct with his advice. Hopefully the copper can be run in an attic. Definitely get at least 3 bids so you know where you stand. Also have the plumbers thoroughly detail how they are going to install the new piping and also know before you sign a contract if ALL work is included to bring your home back to where it was before the leak. You need to understand what your insurance is going to pay for and what is not covered, if you have insurance coverage. Leaks under slabs are handled differently by different companies so educate yourself as much as possible. Once you decide on a contractor and are comfortable with using him.... let him do his thing and stay out of his way. I know that Doctors are somewhat like Engineers in that they want to understand every step and proceedure but let your Plumber do his work. The inspector will see to it that he follows code in most cases.