check engine light is usually an emission problem. bad cat or o2 sensor or could even be a gas cap. i think on that year they only had one 02 sensoe in front of the cat,so the cat can be bad and an 02 sensor should fix. it isn't unusual for the engine oil pressure to read zero on a warm engine on a toyota. what is the oil pressure when driving warm? the ticking could be normal on that model. the rear diff could be going out but that isn't a biggy. doesn't sound like you have head gasket problems to me because it isn't blowing coolant out of the radiator. i would bet you can make a good driver out of it pretty cheap once you get in the right forum.