I understand the confusion now. But I expect that if he is doing this for an oil leak, he probably only needs to do the upper cover. This is the leak prone area.
If he's not familiar with this engine, he may call this the timing cover proper.
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in