Q: How can I tell if the fuel injector is bad or if it is just the o-rings that need to be replaced, without taking them out to check?

Had issues all of a sudden with the car, seemed to happen right after fueling. A few miles later pulling into the driveway the car started sputtering like losing power and then died. The abs and traction control light came on. Tried to restart it and it had a VERY strong fuel smell and white smoke and was hard to start. After smelling the gas we stopped trying that day. Put the scanner on it and ended up replacing a sensor and took care of one problem and the other code said #5 was misfiring. We decided to replace the spark plugs and wires and the mechanic said that there was a lot of carbon and fuel on #5. How can we tell if it is just the orings or if it is the injector itself that needs replaced? Still have fuel smell and white smoke. There is no coolant leaking in, the oil looks fine.

My car has 130000 miles.
My car has an automatic transmission.