My personal take is that you shouldn't be upset with
what was done so much as
how it was done.
Other guys have said it already so I won't beleaguer it: you now have a free, legal exhaust system. I haven't heard any stories of problems with MB's redesigned system ... mine has worked fine, and I've never heard a peep from anyone else about theirs (no news, good news ... you know the deal).
That said ... I like to hope when I take my car in to have something done, I won't find out it's had unsolicited work done on it. My mechanic would never do something like that ... unless it's some $5 switch that needs replacement, he calls me and asks (once he replaced a door check without telling me first ... Ooooo
). I can't imagine a dealer just spontaineously doing exhaust work. Even if they felt absolutely compeled to replace it, they should have called you first. It is your car and you have a right to know. It'd be as if, when I go in to have my tonsils removed next week, I come out of anesthesia to discover they've upgraded my molars to solid gold ones. You just don't do things like that without asking first. Even if it's free. Even if you ignore the morality breach, there's still the matter of competance. The fact that they didn't know what a trap oxidizer looks like would be a concern to me. If they can't figure that out, they probably don't know much about 603s. I know what a trap oxidizer is. It's not a hard part to identify. It's like distinguishing a hippopotomus from an antelope. Liscensed MB techs ought to know, too, if they are going to service my vehicle.
I don't think you should feel like your car's been destroyed. It has a reliable exhaust system that is street legal and better for the environment. But I would be concerned about the level of service you received -- and would receive in the future -- from this particular dealership. I would 1) Talk first to whomever is the head honcho at your dealership. Discuss what happened, who's "to blame," and what can be done to avoid such things in the future. It could have just been one or two techs and it might be a case where the dealership will go out of their way to make amends. Then 2), if you don't get any sympathy or help, file a complaint with MBUSA. I'm not talking lawsuit or major uproar. Just let them know that this particular dealership was not straightforward and did unauthorized work on your vehicle without first contacting you. Again, it's not what they did, it's how they did it.