Please be sure to post the solution you find to help others in the future.

Look below the alternator, there is a similarly sized black round item that is the air pump. For 96 it should be electric powered, older ones were belt driven.

There is more to the system besides the air pump. At the front top of engine ( under the black plastic cover that has a MB star on it) there is a vacuum solenoid valve. Check this and the tubing running to and from. The tube that runs under the coil cover eventually leads to the air diverter valve. This diverter valve lives between the two exhaust manifolds.

I've had the vacuum solenoid to diverter valve line get caught under the coil cover and crushed so have a look there as well.

Also, in the underhood black box ( base of windshield, passenger side ) there is a relay / 40 amp fuse for the pump, check these parts.

$ 1,400 is way big for this job. A used pump would be the way to go if it is bad. Try car-part.com , this is a nation wide salvage yard inventory search.