To replace that trailing arm, you will need to drop the subframe. In brief, dropping the subframe entails supporting the car sufficiently high off the ground, pulling the wheels, disconnecting the driveshaft from the differential, removing the aft part of the exhaust system, removing the springs(proper spring compressor required), pulling the axles (some brake caliper removal reqd), disconnecting the brake lines and sway bars, supporting the subframe, then removing the subframe bushing bolts and lowering the subframe to the ground and moving it to where you can unbolt the trailing arms from the subframe.

When you find a replacement trailing arm, you'll need to install new trailing arm bushings in it. The parts houses provide regular and eccentric bushings. You need the regular ones; eccentric bushings are for a level of alignment that cannot be performed outside the factory or phenomonally-equipped service shop.

Search in here on subframe, trailing arm bushings, subframe bushings and, in particular, posts by dmorrison who knows a lot about the backend of these cars.

Good luck, that's a big job.

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Never a dull moment at Berry Hill Farm.