Here's what I did with mine when I replaced them (very recently):

I did the primary (clear filter first).

1. Note the orientation, pinched off the lines with vicegrips and softjaws.
2. Loosened hose clamps, drained the filter into the new secondary filter canister (didn't want to waste any diesel).
3. Put a new filter in the same orientation, tightened the hose clamps.

Next, the larger secondary filter.

1. Survey the area, figure out how you're going to get it out. Mine's obstructed by the upper radiator hose and a large vacuum hose.
2. With a plan of attack, loosen the bolt at the top of the housing, and slowly extract it from the bottom. If it's like the 300D, the only way out is the front. It'll be extremely full, so, it's worth your time to cover things up with rags, so diesel doesn't get everywhere.
3. Carefully remove the filter, and put it some place it won't spill.
4. Put new o-rings on the banjo bolt. There are two.
5. I put my new filter in place and slightly offset to fill it. If you don't fill it manually, it will take a very long time to fill it by cranking (also, it's hard on the battery and starter). I used a tube and filled mine with powerservice, as full as possible.
6. Hold the filter firmly against the housing and replace the bolt. Tighten by hand, and then snug with a wrench.
7. Remove tools from engine compartment.
8. Crank car. I did about two 10-second intervals. After that point, it started to catch, and I was golden.
9. Check for leaks.
10. Test drive for good measure.

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1982 240D, sold 9/17/2008
1987 300D TurboW124.133 - 603.960, 722.317 - Smoke Silver Metallic / Medium Red (702/177), acquired 8/15/2009
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