First get the car checked by a good mechanic, if the car is silent and has no other noise but the smoke is easilly visible and its bluish white then most probably your car needs a new set of rings/pistons, if only rings (you ll know only after the engine is opened up) then it wont cost much, if rings, pistons both then along with few other parts including gaskets etc. plus machine shop plus mechanic will in total make you a bill of as high as 10k !
Whats the year of the car ? how much it has done and have you maintained it yourself ?