Luke, come away form the Dark Side and channel your anger into positive energy. Try MBUSA to see if you can plead your case with the known defect. Maybe they'll at least cut you some slack on their 500% profit on the new part.
In the mean time look around for a used tranny. There are plenty of wrecked cars where the transmisision is fine. You can also se if yours can be rebuilt. I don't know what's wrong with yours, but $5K will get a lot of rebuild.

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Prost!