Volvo Repair: 92 740 Turbo, impeller shaft, turbo unit

Question
Daughter owns a 1992 740 turbo with 174,000 miles.  Black smoke (very thick) is coming from the exhaust. A mechanic told her the turbo needs replacing and the cost would be $1,000.
The car is mechanically and electrically sound otherwise - is it worth the price to replace the parts? An does all components need to be repalced?  

Answer
Greg, I would get a second opinion.  Tech should check all rubber turbo hoses and do a impeller shaft test before condeming the Turbo.  Yes they fail but if the services are kept up, turbos last a lot longer than 174k.  What all Components are you talking about?  $1000 is fairly reasonable.  Is the Turbo unit new or used?  Let me know.  Roger