Been there done that on two different 300E's 1990 and 1992. If complete exhaust system means Catalytic Converter back then the $960.00 is way high. I went with Eberspacher, which I'm told is OE supplier. Looked absolutely identical to original parts. Looks like current internet prices at about $180 each for Center Resonator and Rear Muffler.

If complete exhaust system includes Catalytic Converter then it looks low. Much caution needed when replacing Cat., or so I'm told by my indy.

Steve