I'm selling off my stock exhaust unit. It is one complete piece, so I'd prefer only locals to inquire as the cost of shipping would be very expensive. It'll bolt right on to the E90 chassis and OEM hangers. No additional parts are required however I recommend that new gaskets (x2 @ ~$24/gasket at the dealer) replace the existing ones before bolting on. The job can can definitely be done on your own. Once your car is in the air its only a matter of knowing how to use a socket wrench to loosen and tighten bolts.
Currently the part is located in Rancho Cucamonga, CA 91701.
I'm asking $300 picked up.