2002 Pontiac Bonneville POSSIBLE FUEL PUMP FAILURE

AFTER THE ENGINE RUNS FOR A SMALL AMOUNT OF TIME THERE IS A HESITATION EVERY TIME YOU ACCELERATE. LIKE ITS NOT GETTING FUEL. I REPLACED THE FUEL FILTER FIRST AND THE PROBLEM STILL REMAINS. IT APPEARS TO BE THE FUEL PUMP (ASSEMBLY??). THE DEALER SAYS THAT THERE ARE PRESSURE SENSORS AND OTHER THINGS THAT NEED TO BE CHECKED FIRST. I CALLED LOOKING FOR A PRICE ON THE PUMP ONLY. THEY WANT TO DO AN HOURS OR SO OF DIAGNOSIS FIRST. WHAT OTHER CAUSES EXSIST AND IF I REPLACE THE PUMP MYSELF, SHOULD THERE BE A DIAGNOSIS PERFORMED FIRST OR I'M I PADDING THE LABOR BILL.