To "check" the fuel filter, you will need to break it open with a hammer like I did. The only thing which will give you a good idea about your fuel filter's condition is the fuel pressure (that hesitation is a VERY good indicator as well). You don't really need to rely on those jackasses for this task. Simply get a cheap fuel pressure measurement kit, or make one yourself. You will need to buy the appropriate size piping, a T connector of the same size and a meter for liquid pressure measurement. You can pull your fuel hose from the car and take it with you to the hardware market for size reference purpose. For exact fuel pressure specs information, consult the service manual. Also, like I said above, don't ignore the O2 sensor. Once it is fouled, the pick can be ruined because a lazy O2 sensor makes the ECU dump loads of fuel into the engine thinking it is still running lean when in reality it isn't. Soaking the O2 sensor in Apple Cider Vinegar overnight and scrubbing with a tooth brush in the morning pretty much completely restores it, unless the heater element inside it is not broken or shorted out.