Manie

Ok so i bought a 92 convertibale 240sx stock ka its auto its been sitting for over 4 years before i bought it and it didnt start so i replaced the ignition switch and starter and bought a new battery and it started. So today i changed the oil and it started pouring out more then 5 quarts and it smelled like gas so i put new oil and new filter and changed spark plugs and it started right up but its leaking something from the bottom of the motor and smelled like gas but it looked like old oil. And the motor shook really bad at low idle. Is the motor bad? Does anyone knows whats wrong?