The eccentric shaft seal is on the top of the valve cover, at the rear. You can pop off the vanity cover and the eccentric shaft seal is the gold looking diamond shaped piece.

Confused what engine you have though - you say it's a 04 4.4 which would be N62, but then say you found that code "after I drill down from the Engine-DDE Diesal Electronics DDE3.0"
The N62 uses an ME9.2 DME. Why are you looking at diesel stuff?

I would just get it smoke tested, and go from there. If there's a leak somewhere it'll be obvious. You can't assume that just because someone else's vacuum leak was from there, that yours will be too. You need to properly diagnose the problem first.