Need exhaust on '84 euro 500SEL, complicated?

[agara]

Okay, got the old brute to pass IL emissions yesterday. Now feel confident I can keep the car and still pass emissions in the future. Now I need an entire new exhaust system, and not sure how complicated this will be. I have found plenty of suppliers for the two major sections, which doesn't of course come with catalytics. The present system is the stock with catalytics welded (spliced) into the middle long pipe section.

Is there anything else that needs to be considered? I assume that the O2 sensor will be in the right place, but are any other parts required? I called up Carlos at C&H and he was willing to take the job, but mentioned taking current readings and checking for other parts such as air pump, position of O2 within system, etc. Any clue as to what I may or may not be getting into?