The steam is normal in cold weather, after running it when the exhaust system is hot the cold wet air condenses in the exhaust system. When you start it up the hot exhaust gases start to vaporize the water that is in there and result is steam. After warm up if the air is really cold and moist you will also get condensation right at the back of the tailpipe, just look at a pic of cars ideling in traffic in NYC.
Stick your nose by the exhaust and sniff it for anti-freeze, if you have a leak you will smell the prestone right away. No anti-freeze smell 99.9% of the time means no leak.
If you do alot of short cycle type driving, limited warm up and never let the moisture in the exhaust cook off you may rust the system out early.
On the oil side if you don't run it for say at least 30 minutes the oil never reaches the operating temp of the motor, result is that the moisture that condenses in the engine, just like the exhaust system, never has the opportunity to cook off or boil off, that will generally leave a light brown or tan residue on the inside of your oil filler cap and if it gets bad enough it will also show up on your dipstick as a brown mix on the highest point of the dipstick.
Here in PA on a cold morning it takes about 9-12 minutes for the thermostat to open and the gauge to reach operating temp, if you stop at that point and shut the motor off, pull the dipstick and feel the oil you will find that it is still not hot, warm maybe, but not hot enough to boil off the moisture, that generally takes about 30+ min to reach that temp and start cooking it off, then it is a matter of how long you drive it that determines how much moisture gets cooked off.