Trade-in value for a sedan in good condition is $70k; a coupe is at $76k. Both of these values assume a stereo is installed and all parts are present and accounted for. I guess to answer your question, the only way to determine if it's worth it is
- How much for replacement seats?
- Why replace the stereo? Put a far superior aftermarket one for around $1-1.5k.
- Carpet cost?
- Labor for all of this?

Assuming the seats are available on the used market at a reasonable price (and probably the OE stereo too), then this car sounds like a deal...big bucks, but a reasonable deal. If it's warranteed, then I'd say go for it. Just be prepared for V12-sized maintenance costs, as I've heard they're scary.

Best of luck!

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Best regards, Michael
'92 500E
'88 300TE