1998 Buick Lesabre should I get a diagnostic

FOR THE LAST MONTH MY CAR HAS BEEN AT A GARAGE. THE FUEL PUMP WENT AND HE REPLACED IT. THE NEXT DAY I TRIED TO GO TO PICK IT UP AND IT STALLED RIGHT IN THE DRIVEWAY OF THE GARAGE AND WOULDN'T START AGAIN. SO HE PUT ANOTHER FUEL PUMP IN THE CAR AND DROVE IT AROUND FOR A DAY AND IT WAS GOOD. I BROUGHT IT HOME AND THE NEXT DAY IT WOULDN'T START SO I HAD IT TOWED BACK. HE GOT IT Back IT STARTED FOR HIM SO HE KEPT IT FOR A WEEK AND STARTED IT EVERY MORNING BUT HE DIDN'T DRIVE IT AROUND. I TOOK IT BACK I DROVE IT TO THE STORE THAT SAME DAY AND BROKE DOWN ON THE WAY HOME. HE'S HAD IT EVER SINCE HALLOWEEN AND I JUST GOT IT BACK AGAIN AND ALL HE DID WAS REPLACE THE FUEL PUMP AGAIN. I'M AFRAID TO DRIVE IT ANYWHERE IT JUST SEEMS TO ME THAT A WIRE OR SENSER IS GONE OR SOMETHING ELECTRICAL THAT HE DIDN'T BOTHER TO CHECK. ISN'T THERE A TOOL THAT CAN CHECK FOR THESE THINGS?