any tips on replacing AZB auto transmission in 92 100S?

I have bought a replacement automatic transmission (AZB) for my 92 100S. The replacement was pulled from a collision wreck and was reportedly working fine
at 92K. Cost $300. Fluid is clean and not any traces of burning. How hard is it to do the job? Any special tools needed besides a transmission jack? Any tips REALLY appreciated. While under warranty this 92 100S had THREE tranny replacements. Is there something that the dealer mechanics missed that is causing repeated failures? I drive really easy, never tow, and have kept other tranmsmissions working for many hundreds of Kmiles with no problems. I know I may be wasting my time putting in a fourth tranny, but I really like the car and the engine is in great shape. Thanks, Mark
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