603 question
 

On the cylinder head next to the exh. Manifold toward the front of the motor what is that round thing threaded into the head

I believe you are referring to the timing chain tensioner bolt....

I'm getting oil on the alternator looks like oil leaking from from tensioner bolt

If the leak is in fact coming from the tensioner assembly there is a large thin aluminum crush washer that seals it to the cylinder head. Double check the leak is from there and not the valve cover gasket above it, the crush washer is a dollar or two from the MB dealership.