That's right Mike, oil in diesels turns black about 5 miles after a fresh oil change. For one, the oil cooler holds about half a quart of the old stuff which quickly mixes in, and diesels generate a huge amount of soot from combustion - the fact that the oil is black means the oil is suspending all that soot like it's supposed to
Not to worry - sounds like it was due for a change time wise though.
Regards,
- Ryan