92 Pontiac bonnieville will not start

hi all here is my situation:

i was driving home and the car just starts to sputter so i had this problem before and it was a spark plug wire so i changed out all the wires and tested the car and it drove fine
so that morning got up to go to work drove the car about 5 miles it started to sputter again but this time it was worse so i park the car auto store was down the street asked them about it (they didn't know anything) suggessted i change the plugs when in a change the plugs. did a test drive and car did the same things sputter so i tried to drive it to a firestone or a goodyear by this time the car was going like 10 miles an hour so the car cut off and wouldn't crank back up so i had it towed to my house so i had my machanic look at it he states that it was the fuel pump so we change out the fuel pump and the fuel filter and the car still wouldn't crank up we check everything we could and now the only other recourse i have is to take it to the dealer and see whats going on with it do you all any other ideas i can try before i tow it to the dealer

oxagen sensor, mine did the same so i changed it and haven;t had that problem since