I got the antenna (now on the nüvi 350) working, but not as it was intended. Reason: there's no way I could possibly solder a 1k resistor on the PCB. The connections on that spot are way too tiny (read: my mini soldering gear is still too big). I therefore went for the alternative repair, and that is to connect the center pin of the external antenna receptacle to the center pin of the internal antenna contact on the PCB, using a thin wire. Still not much room to work, but manageable. Result shown below:

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