There's no guarantee that you will be able to fix, if I remember right the 02 uses a solenoid block that contains all the solenoids which means expensive as just one can't be replaced. Search the forum to see if I am right. Still if that's the problem it's not a hard fix. Can't advise you as I don't know your capabilities, many people don't like messing around with oil. You have to decide. 300 sounds high just for a diagnose.