If you really "reached in and stopped the fan" and it was the engine fan, not the hub of the electric one you shouldn't be doing anything mechanical.

There is no way anyone can tell you (unless its a wild ass guess) what it would cost to bring it back without a lot more information. So, assume the worst: overheat = head gaskets, no gauges = new/used cluster. Already at $5000 if you are paying someone else to do it.

Pass on the car, it should not be your first because it would surely be your last MB.

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Hanno
'79 6.9 Sold (after 27 years)
'83 280SL, 5 spd.
'94 E320 Sdn. 5 spd conversion
'02 E320 Sdn.(on loan to mom!)
'87 300E (5 spd. conversion) Sold
'05 E500 Wagon