As "Big Katuna" asked, what are the symptoms. You don't here about these going bad very often.
Remember, the pick up tube for your generator doesn't go as deep into the tank as the engine pick up tube, so that the generator doesn't run you out of fuel and leave you stranded.
Before replacing the pump, I would get a five gallon container of diesel fuel and run a hose form the generator into the fuel can and see if the generator runs normally. Often the OEM generator hose can go bad or the pick up tube in the tank have been known to get pin holes and cause issues.