Possible oil leak from head gasket or crack in

either bad rings or head gasket

Check camshaft oil seal also if head wasn't skimmed or not torqued down properly & with new bolts it could be leaking out of head gasket

It is important too identify the following:
1) The source of the exhaust leak
2) The source of the oil leak.
The exhaust leak could turn out to be a bad exhaust gasket, a cracked or loose exhaust manifold, a cracked cylinder head or bad gasket, or related parts. The oil leak could turn out to be the valve cover gasket. A dried out valve cover gasket can cause oil to sit on the spark plugs and have oil leaks. Be sure not to over-fill the oil. A machine shop can find cracks in cylinder heads. If these problems turn out to be ok (and one of those stethoscopes may be helpful) then you could procede to check fuel delivery. (there will be pressure in the lines) A lot of times connectors get corroded. I noticed on this model the sensor for the engine cooling mounted near the thermostat is very sensitive to variation. Same for the air sensors if left loose.

White stuff in the water is most likely oil. To test the head gasket, fill the radiator right up to the neck, leave the cap off. warm up the engine untill the top hose gets warm. Then look for bubbles in the radiator, keep it topped right up to the filler top. Continuous bubbles mean a faulty head gasket.
Antifreeze goes in the radiator.

Depending on the extent if the leaks - if it's a simple head gasket have head gasket replaced. It could be cracked head or block then it's going to be more of a job and expense. Id you doubt dealer have another shop look at it.

If you exhaust is constantly emitting white exhaust fumes the whitest color is your coolant being extracted from an internal gasket leaking

All Daewoo Engines are interference fit Engines. Which means that if the timing belt rips while the engine is running the pistons will hit and bend the valves and you will have to get new valves and possibly a new cylinder head. Worst case scenario you will also have to get a new engine block if for some reason chunks or pieces of valve, piston or cylinder head damaged the cylinder bore and cracked the block while things were moving around. Daewoo Timing belts are recommended to be replaced at 60,000 miles but it is best to replace them before 60k as some people have had their timing belts break on them as soon as 61,000 miles.

You will need to replace valve cover gasket and pcv valve.

It is quite possible you have a leaking head gasket or intake manifold gasket... allowing both an oil leak and a pressure leak from the cooling system. The alternative may even be as severe as a cracked block. Get it checked before you drive too much farther!!

There is no radiator cap, the Lanos has what is called a "sealed cooling system", popular on newer model European cars and most Asian models, even some of the latest US made cars. You can squeeze and release the upper radiator hose repeatedly to "pump" some of the air out/water in.

The engine has to be leaking water somewhere. It could be a small leak that only leaks under pressure (when the car is hot) and the water is evaporating as fast as it leaks out. This kind of leak can be very hard to find! I had this problem on my daughter's 2001 Lanos until today, when I found the leak. A heater hose burst today while she was getting gas, luckily the car was stopped! It had been using about a tank full of water every month (about one quart or liter), but could find no leak. I suspected a leaking head gasket or cracked (which could be your problem), and was preparing to take the head off when she was on Christmas break from college. I'm glad that hose burts!

A leaking head gasket or cracked head is hard to detect. Most of the time there will only be a small leak when the engine is hot, and the small amount of water pulled into a cylinder is vaporised as the engine runs. There will be no water in the oil unless there is a large leak. Pull the oil dip stick and look under the oil fill cap. If there is a tan looking substance on either one there is water in the oil and you definitely have a cracked head or leaking head gasket. If it's just the gasket you're lucky -- the gasket will usually only leak if the engine has been run very hot (boiling over and then run a bit), and then the head will either crack or warp. A warped head can be repaired, but must be taken to a machine shop for repair. A machine shop can also check a head for cracks, as the cracks are usually too small to see, and usually only open and leak when the head is hot (normal engine operating temperature).