97 eight eight randomly stalls 3.8

My randomly stalls sputters then stalls. If i let it sit it starts up fine or with sputtering but then it passes and drives fine. I gave my car in to a mechanic and he insisted it was the fuel pump. He said he tested it and gave it power and it was weak.It also generated a code o2 sensor and misfire.He claimed the fuel pump could do that. Well $600 later new fuel pump and filter and new air filter I was driving and it did it again. It started sputtering and died. I let it sit and after a couple of restarts it caught but it was still sputtering like all the cylinders weren't working. It wouldn't go over 5 mph but as I drove like that the sputtering stopped and it started driving normally. It also generated a code random cylinder misfire.

Random stalling can indicate several possible problems. 1. Does the security light come on just before this happens? 2. The crank position sensor is going bad. 3. Bad fuel pressure regulator. 4. Bad ignition module. Start with the security light then fuel pressure check, ignition module and finally crank position sensor. However, if the security light and the fuel pressure check out the crank position sensor is probably your problem.

is there any way of testing it and can a novice but handy change it