How fast does gravity propagate?

Does Gravity propagate instantaneously? In other words, to use a fancy analogy: I move the sun 10,000,000 km in 1 sec in 1 direction, will the earth move instantaneously or will the effect only propagate at light speed to reach the earth 8 mins later?
My feeling is that the effect will be "felt" by the earth instantaneously, due to the fact that Gravity propagates in a field around any body. Apparently the jury is still out on whether Gravity consists of both field and particle (Gravitons) components (sort of like light) but I may have my facts muddled up on this one.
Therefore, accepting that Gravity propagates instantaneously, even at stellar distances, any change, however minute, is immediately discernable. It is then logical that if it is possible to interact with the gravity field of Earth, the Moon or a very large space station, it should be possible to regulate the gravity fields generated by this body. This regulation can then be molded into communication signals that travels the universe around us instantaneously, to be picked up by our own (or alien) receivers without the wait for signals that only travel at the paltry 300,000km/s speed of light, so to speak.
We can start small by trying to regulate (or oscillate) the gravity of a small craft the size of Sputnik, building a working receiver that reads the signal from this source and then working up from there.
Obviously the ability to manipulate the gravity field of any body may be a few (or a great many) years in the future but the theory seems plausible.
Am I totally off the mark here or is there merit in this hypothesis?
Regards
Riaanfrom Menlyn