Hope you got this fixed, If not I got a great aftermarkt cat for my 560 sel from a LA dist. Wasn't cheap ~500$. Noe that I have it, I see you could get it done in a muffler shop. There is one big cat under the cat much easier to weld in that the original which would be impossible to do on the car. I'll bet it might be $200 -$300 in a shop.