W124 602 fuel leak - help please

[speedy]

I shut off the car in my garage this afternoon and 15 minutes later I had a good-sized puddle of fuel under the car. It is dripping from a small aluminum canister that is bolted to the block just below the plastic prefilter. I don't know what this canister is... maybe the fuel pump? It's smaller than any fuel pump I've seen before. I have searched the forum but was not able to find a definitive answer. It has four hoses going to it - one from a device on the side of the IP (fuel heater?) via a hard plastic tube, one from the plastic pre-filter, and two that go to the firewall area.

The hose exiting the front of the canister to the plastic prefilter is where the leak is. The front of the canister looks like a plastic piece that is held in by a circlip. This plastic piece will swivel a bit, which always bothered me. Bad O-ring? If so, is it easy to replace, and where is the best place to get a new one? I would like to get one locally tomorrow (Dallas area) if possible. My wife does not like the strong diesel odor (nor do I).

The car in question is a '91 300D, in case you couldn't guess.

Thanks in advance,

-Dave