How long does it take to replace an A/C compressor on a 2001 1.8L Passat? My mechanic said he did it in 2 hours.

you need to change the filter/drier evacuate the system put fresh oil in your compressor, charge on the low side to 24 psi or whatever the spec is on your system....perhaps your system had a leak and the refrigerant was contaminated with ambient air...probably is still okay if given half a chance~

If the compressor failed badly enough debris from the compressor may have circulated throughout the system. This will require flushing the entire system at a bare minimum. If the system is not flushed the compressor may fail again and any compressor warrenty voided. Depending on what the flushing and inspection of the compressor reveals, it might be nenecessary to replace a clogged condencer and expansion valve in addition to the receiver drier/ accumulator. it might take a while for the debri to lodge and cause blockage or cause a compressor failure. Having all this work done could get very expensive.You might luck out and just replace the compressor. The question is "Do you feel lucky?"