IF YOUR LEAK WAS UNDER THE SINK ON THE DRAIN, this is something that ANYONE can do, with the PVC plumbing, no tools required. Either 1) nut was loose (ONLY hand-tighten, never tools on PVC to tighten) or 2) plastic donut gasket snapped/ cracked and needs replaced. RARELY HAPPENS, BUT DOES AND WILL CAUSE THE LEAK.
The reason I say everyone needs to know/ be able to is because this is where the diamond ring goes when you drop it in the open sink
** The donut slip-joint gaskets have a taper on one face that must match/ meet the taper in the pipe or if installed backwards, will leak.