I wouldn't spend too much time poking around now. The engine needs to come out, get it out and take a look when it's out ... everything is much easier that way. M54's are cheap. Find a good one and plop it back in. You can use ANY M54 - you'd want to keep it 3.0L due to the weight of the X5. But you can use a RWD variant and just bolt your oil pan and accessories onto it.