1993 Geo Prism pinging

1993 Geo Prism Lsi 1.8L mileage: 79,400. Recently I had replaced all three of the accessory belts, along with the timing belt. (I had to get it fixed twice because the first time the independent auto shop did not put it right and I had subtle loss of power and minor vibrations while idling and then I got the timing belt done from The dealer.) (The accessories belts are still from the independent auto shop) I hear like a shrill radio static or crackling of electricity (is this called pinging? I sometimes get a very low noise like striking glass bottles.) These noises only happen when I press the gas pedal between the speeds 30 and 55 mph. (It does not come above 55 mph) and only after driving for twenty mins. I did find that the mechanic had forgotten to connect the Air Mass Flow sensor to the Air Filter Chamber, which I promptly connected (but I still get the noise). Also, when I turn off the engine I get a short squeaking noise (again after fifiteen to twenty minutes of driving.) The dealer says it seems to come from the alternator bearings. My question is: What may be the cause and cure for this problem? Can I put grease or something in the alternator bearings? Also is my oil pump working properly? (Reason for this question being four weeks back my oil light had come on and I immediately showed it to my mechanic who found a wire had come out of the oil sensor and had fixed the wire back to sensor.) Will my car run if the oil pump was not working?