the BIG TRICK is to properly seal the upper timing cover, by doing what the manual says not to do!!!!!
When you install the U-shaped rubber seal between the upper and lower covers
SLATHER THE WHOLE SEAL WITH SEALANT, not just the corners.
Trust me on this; I fought that seal for almost 30 years before I tried it, and no more leaks at all. Any decent black sealant is good (Permatex, etc), there's no magic about the European stuff. Of course, cleanliness is BY FAR the #1 criteria.

Cheers,
DG