I have a Nissan Altima 1998; I have bought it recenlty... There is a sign telling me "Engine Service Soon!" What does it mean? Plus, the gas meter seems does not move! The needle on the gas meter does not move or barely moves! What shall I do?

For the check engine light soon light, u can go to any pep boys and they can tell you what the car needs, using their code reader, and it's free. If not, then maybe you could find another auto parts store who will do it for you for free. Now for the gas gauge, it could be the sensor inside the gas tank that sends the signal to the gas gauge.