You should not go for engine swap. It's costly, involves risks and requires advanced skills to be accomplished successfully. Every tom, dick and harry can not do this job. Plus, there are fewer chances that you will get a quality used engine. Now, the problem you have mentioned is not a major problem. It happens with cars when engines ages over the period of time. What you need to do is look for these issues:
1- Check whether car is leaking oil from somewhere. Sometimes, cars leak oil when they are moving and not stationary. Get under the car and see oil debris to find out any leak.
2- Since you have mentioned smoke issue, that could be due to weak piston rings, valve seals, leaked gasket, bad air filter etc. Such things can be fixed easily by a practised mechanics. Engine overhauling will cost you much less than risky engine swap. While your original engine will be opened, you can take care of other worn out parts as well. Finally, you will get a better performing engine of your own car.
3- Check the power of engine. Do you feel any lag in performace, missing, poor pick, engine overheating etc. When engine has gone weak, you will observe the signs of weakness while driving. Check the spark plugs, radiator coolant for the presence of engine oil in it, check exhaust for leaking engine oil to be assured about the actual issue before making any decision.