There are 3 primary causes for oil leaks on a 7.3L diesel. The most common for large amounts of oil loss are the HPOP O-Rings that are located at the ends of the fittings that screw into the HPOP. These can be repaired at home with a 9/16th wrench and some time... the O rings are cheap/free at your local autoparts store. You can identify this leak several ways. Oil in the valley, behind the hpop but ahead of the turbo is a key indicator. You can take a rag and wipe the underside of each fitting clean, then start the truck and run it. Sometimes you'll need to rev it or drive it a short period to increase pressures. Check again with a clean paper towel or rag and if there is new oil, you've found your leak. Additionally check the fittings themselves as well as the stainless steel braided lines that run to the heads.
The next most common oil leak are the turbo pedistal O-Rings. There are a total of 4 of them in 2 different sizes. This requires the removal of the turbo, and instructions to do so are here
. There are two (black) O rings on the top, and two (yellow) O rings on the bottom.
Finally the pedistal itself has a rod connected to the back pressure valve that is oil actuated and is known to leak. You can cure this one of several ways. You can gut the pedistal
and plug it, or install a new pedistal (with or without the rod is up to you!).
Honorable mentions include the IPR, HPOP gaskets (there are two, one between the front cover and the resevoir and the other is between the pump itself and front cover), and ICP sensor. Finally - the rear main is one of the LAST places that fail or leak on 7.3's.
IF you do fine the leak, I've found this link to give alot of kits...
DFUSER Diesel Performance Products Exhaust High Performance Part Diesel Intake Diesel Power Chips