I kind of agree with most of the comments so far. My perspective when I decided to have my gearbox refurb'ed for c£3k was really less about what I would get for the car, and more about how long would it last if I fixed it, and what would the cost of driving something comparable be.
On that basis, spending £3k (with a 100k/3 year warranty) seemed to me like a reasonable investment compared to the £10k+ that it would've cost to put me in something that was even close to the s8. However, I do use my car quite a lot, and three grand is still quite a lot to shell out on an old car with an uncertain future in terms of further bills.
So I'd say that if you're likely to keep it, want to continue to drive a car of this quality, and can find the funds to do this, then it's worth it. If any of these don't apply however, then you'll probably be moving it on, and at least there will be people here who'll be interested in (parts of?) the car...
