As noted the assembly in the center of the air cleaner is a device that is intended to separate the oil droplets from the gasses that make up the "blow by" that is fed from that uncovered hole in the top of the valve cover in one photo to the air cleaner assembly. As the volume of blow by grows for a variety of reasons, the capacity of the cyclone separator is reached, then overcome, and it leaks some oil into the air cleaner. The capacity is somewhat reduced when it fills with oil, so cleaning it out may reduce the amount of oil that is dripped into the air intake. The same is true with the drain line - over time it can become contaminated with junk that mixes with the oil and sticks to the tube and reduces its ability to drain away the oil that is collected. Changing to a synthetic oil may also be beneficial (it flows better as it cools off). In a practical sense this is not worth getting upset about enough to do much more than cleaning out the parts and trying to keep leaks to the outside of the engine and onto the ground to a minimum.

The oil cooler line is also likely not something you want to do much about unless the leak is offensive to you - it will drip on the ground and make stains, etc. Fixing it is a significant chore and will likely involve a new cooler and set of hoses (can run over $500 in parts alone). On my car the problem became more than a housekeeping issue when the bottom of the cooler blew out due to rust. In that case there was little choice.

In general the black rubber suspension parts don't like being dunked in oil, as noted above. They soften and begin to disintegrate. A good car wash that also addresses the underside of the car will help here.

This site has loads of virtual experience to offer. So, if you want to keep it as a beater or restore it, keep asking questions. In the end, it is likely the enthusiasm from the members will have you fixing it up to be at least mechanically sound in no time. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)