I am considering purchasing a 2003 SC430 with a broken timing belt. The heads are off the block, and would need to be rebuilt before they could be used. Should I purchase a used engine from www.car-part.com, or just purchase two used heads? I successfully replaced the head gasket on my 530i, so I think I could complete this project. Does the engine come out the top, or out the bottom like the Porsche Cayenne?