if you can pull the intake tube off the turbo, you should be able to spin the turbine by hand, and feel for play, or binding. if it spins freely, or slightly stiff, the turbo is likely good. if there is a lot of up/down or in/out play, it is worn... if anything binds, it's bad.
you could be lucky, and he may not have changed the fuel filter...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!