I will say you should build the $10 code reader that was all the rage here a few years back (search arthur dalton's posts) and see if you get some meaningful info (codes) to verify the dealer claim. Obviously it is cheaper to just replace most of the components that could trigger the check engine light than to replace that thing (unless you're in a state where you need it for emissions). At 200K miles, if it's running well you can just tape over the light.

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Prost!