There shouldn't be any degradation in performance. What your engine doesn't have is the ability to reduce fuel if the turbo were to blow too hard, say if the wastegate stuck open.

If I remember correctly, the sensor has a bullet plug. If that's gone then you might need a new sensor. There's nothing special about the wire. You can make it out of parts from Radio Shack.

Check the parts forum to see if anyone's parting out a 300D or 300SD of that vintage.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD