1. Neutral is neutral...wheels can spin.
2. The cable in the engine bay for the tranny adjustment might have just been the kickdown or throttle linkage. I had what I believed to be a flaring tranny fixed by replacing a worn clip on my darned throttle about 24 hours after I bought my 190E.
As for the apprentice turning it fast and driving it...let him do his deal. Better to have him hear a bad bearing/bushing/or ball joint and fix it now, while you are there.
Enjoy and keep asking the questions.
John J. Meadows
'83 300D 3.0L 260k mi.
'85 190E 2.3L 99k mi.