Short answer, yes.
I would hold off on agreeing to that work until you get a little more info yourself on the subject from this site. Funny that with extended warranty they pick the thing you have to pay for.
No CEL points to cleaning specifically, most point to a range of items that are to be checked.
Another dealer's opinion would be wise if you are not a DIY type, also useful to get CEL code they read and post it here for comment. It was probably a code that indicates "insufficient EGR flow".
I can add more later and I'm sure others will.


98 Mystique LS v6 atx 110,000km
97 Contour LX v6 atx 125,000km
stock CD on LS, cass on LX
spoiler, tinted windows on LS only
4 wheel discs on LX only
All other available options on both