Perimeter Irrigation Pipe Repair & Relawn

I have a 9 m × 5 m lawn and the irrigation line that runs around several sides has started to leak in a number of spots. The existing pipes sit a little too high, so while we are fixing the breaks I’d like them dropped to the proper depth before everything is closed up again... (Budget: $30 - $250 AUD, Jobs: Gardening, Landscaping, Plumbing)