I think that the 124s have electronic control of the turbo wastegate, and the earlier 190D Turbo (1987 only) has a mechanical wastegate. A friend of mine is having trouble with the electronic control of the wastegate on his 1992 300D 2.5 Turbo. It occasionally won't make any boost, and then correct itself for no reason at all and run perfectly. The 190 should never have this problem.

$3500 Canadian is a great deal if everything checks out OK.