Put two power heads in. One on the left side, and one on the right side. Make sure they are rated for your 90 gallon tank. One will be towards the front of the tank, and one towards the back. Mine is set up as one power head on the front left side of my tank pointing up towards the surface, and another on the back right side of my tank pointing down towards the sand. Creates a circle current around the rocks and does not allow stuff to settle.
Should be able to get any of the sand you want at most pet stores. Got mine from a pet store. You don't need to get the same sand, there is much different looking sand to choose from. Just mine was Fiji pink, but you can get some other color or look you like.
Fish Sticks, the best thing you can do with your dead fish.