1998 Nissan Maxima 6 cyl Front Wheel Drive Automatic 155 miles

My car wont start after driven few miles. But will start without any problem in the morning. The engine would crank but wont fire. I recently had new fuel filter(after market)installed and spark plugs replaced.
My mechanic says it signals that fuel pump is close to finshing its life but would like to change pressure regulator first and see if it helps. If not then change the fuel pump. Very expensive to go this way.

PLease help. Thanks in advance