Symptoms were a small idle ticking noise in the engine that progressed into a larger ticking noise.
It doesn't sound all that bad from what I can tell, How long have you been driving it for in Poland? I take it came from the US, My bet is on it sparking late due to the difference in fuel quality EU - USA.
Is it down on power or anything as it could also be something as simple as a coil pack. My Audi did a similar thing when I had one blow. They are usually really easy to replace and quite cheap. 150 pln max and about 10 minutes to fit.
If its noticeably down on power and running lumpy its more than likely the coil pack, If its driving ok but just making the noise get the timing adjusted and maybe change the spark plugs as the gap may be different to aid combustion, 30 min job max and no parts required.
For the 3000 pln they are asking you could get a new engine, Another sad example of poles trying to rip off foriegners.
If you can send me as much info as you can i'll call my mate whos a mechanic, ie engine size etc, If you know the engine code ie (BMW M50 series) Mileage would help too as he might be able to find out what common problems are with similar models of that mileage.