Is the force of gravity instantaneous?

Its maximal speed is actually c according to Einstein. He predicted the existence of gravity waves that would travel at the speed of light. Therefore, if an object was suddenly converted into energy or matter (I dont know... Super Nova maybe??) the change in mass would create a wave and the gravitational effects would travel at the speed of light.

Forces propagate at c. But they are interactions between some kind of charge (e.g., mass, electric charge) and space. The charge emits exchange particles that alter the surrounding space, and any similarly charged particle, entering that space, must deal with the changes that had been imposed by the first charge.

Of course, the same thing goes the other way, with the first charge having to respond to the effects on space imposed by the 2nd charge. The charges "curve space," but the effect is similar to each mass acting on the other.

That's why there's no delay-torque that destabilizes planet orbits by changing their angular momentum. Although the force propagates at the finite speed, c, the correct influence of the sun's gravity is already established in space when the planet gets to any particular point.

No, the force of gravity can't exceed the speed of light.

Gravity has a constant speed of acceleration.