My former gardener did not do as we agreed he would do for what I paid him to do!

( A drip irrigation system )
Yet I don't want talk about him....
I want to do what I originally wanted in the 1st place myself, but I have no clue how or where to start?
So looking for info so I can start buying the parts I need.
1/2 my hedges are dying from lack of water & I wonder can I use the current worthless for hedges sprinkler line to add my Drip System to?
Or do I need to tear it all out & start over again?
I am a 1st time home owner of 11 months now, so everyday is a learning experience that I've grown to love.