There are two pumps in order to do the following:
Pump #1 feeds Pump#2;
Pump #2 builds the pressure for the CIS system.

A used set of pumps costs about $115. I got mine from SilverStar Recycling in Rancho Cordova, CA, and I got a "lifetime guarantee" of more used fuel-pumps.

I got mine from a low-mileage (45K) 1995 W124 wagon.

Good luck,
:-) neil