First, the oil leak come from the oil filter neck junction, it's a small
gasket, they dry up, nothing to worry, it's a pain in the but job because
the heater box have to be remove so you can remove the fan housing. OR, it's
those 2 little O-ring for the oil cooler. anyway, for both the fan housing
as to be remove. (i have 15 picture of that but i had no time to put them
online! I could find thoses if you need and e-mail them to you.
It's a VW Bus engine, they leak!!!!!! (except mine because am crazy!)

>>>There are some strange knocks in the engine when it is cold (cam slapping
around or something i don't like to think about it much)<<<

Cam don't usually "knocks", crank or rods does! But hey, you know better!
If the noise seem to come from behind the cooling fan and the sound is
"Deap", it for sure a big part but if the sound is more like a "clattering"
(excuse my poor English) it could be those stupid hydrolic lifter...

Good luck, Ben
http://www3.sympatico.ca/huotx/engine1.htm