I believe they are wrong about the conductor plate. If the VALVE BODY is replaced you MAY have to replace the computer, also if the TRANSMISSION is replace you MAY have to replace the computer, there is a chart they should have which will give them this information.
What they've located in the pan is really the "Y" in the road as far as if the transmission is junk. Is this a dealer that has the car?
Metal particles larger than about 1mm (chips and shavings) are usual indicators of recommendation for transmission repair or replacement. I have a book detailing what type of findings are acceptable, if you want I can quote what it says. There are also pictures but I have no scanner and they're not the best pictures anyways.