New owner! 1987 300D

[BLACKCDI]

I also own 2005 E320 CDI but today I picked up 1987 300D with around 200k miles for $2000 as my commuter car in Bay Area, CA
The paint is rough but interior is close to perfect. All electrics work, including sun roof. Engine never overheats 80-90c in all conditions, even while climbing a very steep hill. Tranny shifts smooth.
Suspension needs work, the steering wheel does not stay straight after the turns on the highway(tie rods?) Seems to be down on power when cold, but is OK after worm up. Ac works but the center vents don't. There is a oil leak in the front of the engine.
Questions, is there only 2 speed adjustments for AC? And how do you turn it off, no snow flake button?
Is there a way to make the engine more quiet? (I got spoiled with the CDI i guess..)
The last thing, I occasionally smell diesel exhaust inside the car while driving, is this normal?
Thanks!