Chevy Suburban Rebuilt Engine/Oil Pump

2004 Chevy Suburban had a rebuilt engine almost
2 years ago.  About 6 months ago oil pressure
light went on and the pressure only goes up when
accelerating.  Took it to a local shop in our new
area and they ran a pressure test, confirmed oil
pump needed to be replaced.  When they dropped
the pan there were a ton of metal shavings in the
oil.  They replaced the oil and put everything back
together without replacing the pump, said it
wasn't worth it.  We're in a very small county town
and its really hard to find a shop with the
knowledge of engines for a second opinion.   
Should we get the oil pump replaced?  Or due to
the metal shavings is it really pointless?  We
already spent $4000 for the rebuilt engine so
another engine is not an option