Transmission leaks

tach,
My gearbox (A8 4.2 Bj. 95) leaks. I noticed the oil burned through the stench. The drive hurls the leaking oil against the exhaust at the front right. Now the inclined screwdriver could believe that you change (or let change) the Simmerring and everything will be fine. My father (has a 1a car service) then telephoned with a gear spec who told him that this would be a known problem with a wave that wanders out. If you would change the simmering now (which is quite elaborate), you would have the problem again a short time later.
Then I read here (and elsewhere) in the forum the various gear threads, which suggest a repair directly by ZF (quality and costs).
Now my questions: Is the problem known? Has anyone ever solved it, or? have it repaired by Audi or ZF and if so, what did it cost? The ZF representative here in Hamburg only offers replacement of the gearbox. But I would prefer a repair solution, because I still have a used car insurance and this wage complete, parts but only 40% still pays.

Thank you in advance and greeting
Stefan