I would think that yours would be the same as a 90 124, not sure. But, take the sump cover off, suck out the fluid that is in it, which will expose the filter at the bottom. When you took the cover off the first thing you will see is a small nut in the center of the sump holding down a white nylon or plastic piece about 2 inches long which is holding down a spring, which is holding the filter down. Remove the nut without dropping it, remove the white plastic piece than the spring. You will see the round filter laying at the bottom. Get a pair of needle noise plyers and remove it. Reverse to install. Filter should cost about 3$ or $4. Refill with MB fluid. Hope it works for you.

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Rich

1990 300CE
71 Chevelle SS 454