I have a 99 Passat. How do you know if the motor is blown or the turbo is gone?

Common problem with the 1.8T is sludge build-up in the engine. Which
will eventually find its way to the oil pick-up screen in the oil pan.

Removing the oil pan and cleaning the screen can save the engine.

A chemical flush to remove the remaining sludge in the top of the
cylinder head is also recommended. A couple of oil & filter changes
after the chemical flush, ensures that the filter does not get plugged-up
and bypass the sludge to where it is not supposed to be.

After cleaning, stick with a high quality Synthetic Oil that is
*** VW Rated/Approved for your engine *** to prevent future sludging.

A bad turbo will make noise when spooling-up or blow oil into the
exhaust causing lots of smoke.

Thomas

If it is running to warm up, the engine isn't blown. Follow exovcds advice. Also, you should check the oil pressure to make sure it is within spec.