Apart from takeoff and steering, does a spaceship require fuel to forward itself. No obstructions?

Yes, it would have to be quite a long way from any large bodies like a planet, moon or star though, as they have an influence over all nearby objects (even of they are not directly in their path), causing them to accelerate, decelerate or alter the direction of the object.
In deep space with no nearby large bodies or obstructions an object will continue for the duration of the universe, however this may not be the same as an infinite amount of time.