2001 Ford Taurus over servicing of engine oil -- now smokin

My wife checked the oil and said there was none, so she added 5 quarts and did not look at the dip stick after adding the oil. When she pulled into the driveway, I could smell oil burning. She started the car and there was a huge cloud of smoke from the exhaust. I started it up and push the gas pedal, the engine was bogging down and losing power. I shut it off and checked the oil, the dip stick read about two inches above full. I drained the oil and re-serviced it with the proper amount. I started it up and still smokes a lot and engine loses power when I push on the gas. Previously, the engine did not smoke. What damage to the engine would result in over servicing the oil by several quarts and driving 10 - 15 miles? Are the valve seals and other oil seals damaged? Piston rings? Is the power loss due to the spark plugs being fouled out? What do I do next? HELP.