1996 FORD TAURUS SHO Electrical System Problems

I PURCHASED MY '96 FORD TAURUS WAGON IN '99. I HAD IMMEDIATE PROBLEMS WITH THE SERVICE ENGINE LIGHT A MONTH AFTER PURCHASE. THE LIGHT WAS CHECKED AND I WAS TOLD NOTHING WAS WRONG AND THE SYSTEM WAS RESET. MONTHS LATER, THE LIGHT POPPED ON AGAIN AND I WAS TOLD IT WAS THE OXYGEN SENSOR (BY FORD MOTORS). 6 MONTHS LATER, THE ENGINE LIGHT CAME ON AGAIN AND THE DEALER TOLD ME IT WAS ANOTHER SENSOR. MONTHS AFTER THAT WAS REPAIRED THE LIGHT WOULD COME ON AGAIN AND UP UNTIL THIS DAY (12-17-05) I STILL HAVE PROBLEMS WITH THE CHECK ENGINE LIGHT/ INDICATING A PROBLEM WITH AN OXYGEN SENSOR. I ALSO HAD PROBLEMS WITH THE TRANSMISSION DOWN SHIFTING WITH A JERK WHEN COMING TO A STOP AND TAKING OFF WITH A JERK--- AFTER 8 MONTHS OF PURCHASING THE CAR. ITS WAS COVERED UNDER THE WARRANTY BUT AFTER THE REPAIR--THE CAR CONTINUED...