Is the noise when it is washing or draining water. Your dishwasher has two separate motors and pumps, but they generally run at different times. So if the noise is during the wash cycle, the wash pump would be the problem, if during drain, then the drain pump. If you haven't checked that one out, it is usually where the items like toothpicks or pieces of broken plates end up and then bounce around with the impeller.

If you cannot locate anything that might be making the noise, then the pump is possibly damaged. To remove, you need to pull the dishwasher from the cabinet, lay it on it's back and the motor assembly is held to the sump by a clip and two screws. Remove the screws, pull the clip and the motor slides out the side. You may be able to get a better look and see if you find anything. Otherwise, replacing the pump is just the opposite of removing it.

Sounds good.